ENVIRONMENTAL SCANNING ELECTRON MICROSCOPY

ENVIRONMENTAL SCANNINGELECTRON MICROSCOPY

An Introduction to ESEM®

Philips Electron OpticsEindhoven, The Netherlands

2nd printing

Ó 1996 Robert Johnson Associates. World rights reserved.Robert Johnson Associates2111 Sheffield DriveEl Dorado Hills, Ca 95762

“ESEM” and “Seeing Things You’ve Never Seen Before” are trademarks of PhilipsElectron Optics registered with the United States Patent and Trademark Office.

Contents

PREFACE V

1 INTRODUCTION 1

1.1 What is an ESEM? 1

1.2 What can it do? 1

1.3 This Primer 31.3.1 Terminology

2 SEM BASICS 5

2.1 Description 5

2.2 Imaging Principle 6

2.3 Electron Optics 72.3.1 Lenses2.3.2 Apertures2.3.3 Beam Current

2.4 Resolution 92.4.1 Spot Size2.4.2 Volume of Interaction2.4.3 Signal Type

2.5 Depth of Field 12

2.6 Microanalysis 12

2.7 Why an ESEM ? — SEM Limitations 142.7.1 SEM Vacuum Constraints2.7.2 Sample Constraints

2.8 Summary 17

3 THE ESEM 18

3.1 Vacuum System 183.1.1 Multiple Pressure Limiting Apertures3.1.2 Beam-Gas Interactions3.1.3 Imaging Resolution

3.1.4 Imaging Current

3.2 Environmental Secondary Detectors 253.2.1 ESD3.2.2 GSED3.2.3 Charge Suppression

3.3 X-ray Analysis in the ESEM 283.3.1 Lack of Interferences3.3.2 Sufficient Excitation Energy3.3.3 Skirt X-rays3.3.4 Environmental Gas X-rays

3.4 Summary 30

4 LOW VACUUM - CONVENTIONAL SEMS (LV-CSEMS) 31

4.1 Vacuum Systems 324.1.1 Single Pressure Limiting Aperture4.1.2 Performance Limitations

4.2 Signal Detection — BSE only 374.2.1 Resolution4.2.2 Charge Suppression4.2.3 Sensitivity to Light and Heat

4.3 X-ray Analysis 38

4.4 Summary 39

5 APPLICATIONS 40

5.1 Nonconductive Samples - Uncoated 40

5.2 Hydrated Samples 42

5.3 Contaminating Samples 44

5.4 Delicate Samples 45

5.5 Coating Interference 46

5.6 Phase Transitions 46

5.7 Hydration Processes 47

5.8 Oxidation/Corrosion 48

5.9 Thermal/Mechanical/Chemical Stress 48

FURTHER READING 55

BIBLIOGRAPHY 56

Preface

Typically, inquirers into Environmental Scanning Electron Microscopy (ESEM®) comefrom one of two groups. The first group are experts in their own fields but not inscanning electron microscopy (SEM). They simply have something very small that theywould like to see. They may have been told that they cannot look at it in an SEM. Theyneed to understand how the ESEM is similar to and different from other SEM’s, beforethey can decide whether it will solve their problem. With this same understanding theyare forearmed, if needed, to champion the ESEM against the prevailing wisdom ofconventional SEM. The second group are experts in SEM. They need to reconcile theextraordinary performance claims of the ESEM with the fundamental principles of theirscience, before they will reexamine their beliefs about its capabilities and limitations.We will try here to address the needs of both groups.

Frequently, when addressing a group of microscopists, experienced and neophytealike, we see among them quite visible expressions of what we have come to call the“Aha! Experience” — “Aha! I didn’t know you could do that,” or “Aha! That means Icould ...” our slogan, “Seeing Things You’ve Never Seen Before®,” comes directly fromone customer’s “Aha! Experience” during a demonstration. We have written this briefintroduction to ESEM hoping to promote a broader understanding and appreciation ofthe ESEM’s remarkable capabilities. If reading it brings you one “Aha!”, then your timeand ours has been well spent.

This is not the work of one person but of many. Special credit and thanks are due toRalph Knowles, Philips/ElectroScan Vice President for Research and Development, andTom Hardt and Trisha Rice, of the Applications Laboratory, for their technical adviceand review; Deidre MacDonald for her unerring sense of aesthetics; and perhaps mostimportantly to Ed Griffith and Al Pick for their guidance (sometimes relentless) towardthe goal that this work must serve, first and foremost, the needs of the reader. Of coursethese contributors cannot be held to account for the way I have used their good advice.All responsibility for remaining errors and omissions is ultimately mine.

ROBERT JOHNSON

Would to God your horizon may broaden every day! Thepeople who bind themselves to systems are those who areunable to encompass the whole truth and try to catch it by thetail; a system is like the tail of the truth, but truth is like alizard; it leaves its tail in your fingers and runs awayknowing full well that it will grow a new one in a twinkling.

—IVAN TURGENEV TO LEO TOLSTOY (1856)

As to science itself, it can only grow.—GALILEO, Dialogue (1632)

1

1 INTRODUCTION

1.1 WHAT IS AN ESEM?

Scanning Electron Microscopes (SEM) began to appear commercially in the midnineteen sixties. Because of their performance advantages over other types ofmicroscopes, they quickly became an indispensable tool in a broad range of scientificand engineering applications. Although SEM manufacturers continued to refine thetechnology and made steady improvements in performance and usability, the SEMremained fundamentally unchanged for nearly twenty years. Throughout that time, theSEM’s primary limitations, as a general imaging and analytical technique, were therestrictions it imposed on samples by requiring a high vacuum sample environment.Samples had to be clean, dry and electrically conductive. The vast body of techniquedeveloped for SEM sample preparation is a tribute to the ingenuity and tenacity ofmicroscopists in the face of these high vacuum constraints.

The mid eighties saw the development of the Environmental SEM or ESEM®

(usually pronounced “ee-sem”). Perhaps it would have been better named the VariableEnvironment SEM since its primary advantage lies in permitting the microscopist tovary the sample environment through a range of pressures, temperatures and gascompositions. The Environmental SEM retains all of the performance advantages of aconventional SEM, but removes the high vacuum constraint on the sample environment.Wet, oily, dirty, non-conductive samples may be examined in their natural state withoutmodification or preparation. The ESEM offers high resolution secondary electronimaging in a gaseous environment of practically any composition, at pressures as highas 50 Torr, and temperatures as high as 1500°C.

The ESEM has opened to SEM investigation a whole host of applications that werepreviously impossible. Equally important, it has eliminated most of the samplepreparation required for those applications that were already possible.

1.2 WHAT CAN IT DO?

The examples on the next page offer a glimpse of the dramatic new capabilities of theESEM. The reader with a background in electron microscopy will quickly realize thatnone of these micrographs could have been taken with a conventional SEM.

ENVIRONMENTAL SCANNING ELECTRON MICROSCOPY

2

We will return to a more thorough survey of ESEM applications later. For now, itmay help to categorize the areas of application where the ESEM has significantadvantages.

Gas ionization in the sample chamber eliminates the charging artifacts typically seenwith nonconductive samples.

The ESEM can image wet, dirty, oily, outgassing samples. The contaminants do notdamage the instrument or degrade image quality

The patented Environmental Secondary Detector is insensitive to heat. It can acquireelectron images from samples as hot as 1500°C.

Figure -1-1. Left -Uncoated ultrapure

silicon nitride, aninsulator. Note the

lack of chargingartifacts. Right -

Crystals of table saltdissolving in watercondensed from a

water vaporenvironment.

Nonconductive

Contaminating

Hot

Left - Live green aphid ona rose leaf

Right - Iron oxidizing inthe chamber at 800°C.

Left - Potassium chloridecrystallized from gas inthe chamber at 600° C

Right - Droplets of oil andwater on an oil field core

sample

INTRODUCTION

3

The detector is also insensitive to light. It can image incandescent, fluorescent andcathodoluminescent samples without interference. With an accessory light microscopethe ESEM can provide simultaneous optical and electron images. Its viewport andchamber illuminator may be used during secondary electron image acquisition.

Delicate structures often do not survive the sample preparation required for conventionalSEM’s. The ESEM eliminates the need for conductive coatings, and most other samplepreparation.

Wet samples need not be dried before viewing in the ESEM. This is especially importantfor specimens that must remain hydrated in order to retain their structure. The ESEMcan provide a saturated water vapor environment, keeping samples fully hydratedindefinitely.

Coatings applied during sample preparation may mask valuable information. Forexample a gold coating may enhance surface detail but mask internal structure. Theprocess of applying the gold may itself create artifact in the sample. The ESEM does notrequire samples to be coated.

The ESEM can acquire X-ray data from insulating samples at high acceleratingvoltages. This eliminates the potential for X-ray interference from conductive coatingsand the need to analyze complicated L and M X-ray lines at low voltages.

Much of specimen preparation for the conventional SEM is directed at “fixing” thesample, ensuring that it will not change during image acquisition. Eliminating the needfor sample preparation, particularly the need for conductive coatings, opens a whole newrealm of investigation in dynamic processes. Tension, compression, deformation, crackpropagation, adhesion, heating, cooling, freezing, melting, hydration, dehydration, andsublimation, are but a few examples that come to mind. The ESEM can observe andrecord these processes directly, as they happen.

The sample environment of the conventional SEM is, by definition, empty, a vacuum.The ESEM may be best understood as a microscopic experimental chamber — a labwithin a lab — in which the sample environment can be a component of theexperimental system. Interactions between the sample and its environment constitute yetanother new universe of potential applications. Consider hydration studies in whichsamples are wetted and dried by water from the environment, crystal growth from thegaseous environment, corrosion, and etching.

As this listing demonstrates, it is difficult to neatly categorize all of the uniquecapabilities and applications of the ESEM. The simplest statement might be “All thethings a conventional SEM cannot do.” But neither is this truly adequate since itpresumes a knowledge of the capabilities and limitations of conventional SEM’s.

Light Emitting

Delicate

Hydrated

Masked

X-ray

Dynamic

Interactive — A LabWithin a Lab


4

1.3 THIS PRIMER

In this brief primer we will try to provide a basic understanding of the physicalprinciples and design considerations behind the ESEM. You need not have any previousbackground or experience in SEM. If you do have knowledge in this field you may findsome sections too elementary — feel free to skip them. We hope that you will finish witha solid understanding of the ESEM’s capabilities and limitations, and the differencesbetween it and a conventional SEM.

This latter point has recently become somewhat confused. The ESEM is in factunique. Patents protect the essential aspects of its technology. In response to the ESEM,a new class of microscopes, generally known as Low Vacuum SEM’s, has appeared.These are essentially conventional SEM’s that have been modified to permit limited lowvacuum operation. They have neither the range nor the flexibility of the ESEM but doextend, somewhat, the utility of the conventional SEM. We will devote considerableattention to understanding their capabilities and limitations as well.

From this point on we will use the following terminology:

SEM All Scanning Electron Microscopes.CSEM Conventional High Vacuum SEM’sESEM The Environmental SEMLV-CSEM Low Vacuum adaptations of CSEM’s.

The next chapter reviews the principles that apply to all SEM’s and the limitationsof conventional SEM’s. Chapter 3 explores the unique principles and design of theESEM. Chapter 4 examines low vacuum SEM’s. The final chapter presents a selectionof ESEM application examples.

1.3.1 Terminology

5

2 SEM BASICS

SEM’s enjoy a tremendous advantage over other microscopies in several fundamentalmeasures of performance. Most notable are resolution — the ability to “see” very smallfeatures; depth-of-field — the extent to which features of different “heights” on thesample surface remain in focus; and microanalysis — the ability to analyze samplecomposition. In this chapter we will examine how an SEM forms an image and theprinciples that determine resolution, depth-of-field, and microanalytical capability. Wewill also look at the different signals available in the SEM, particularly as they relate toimage resolution. We will conclude with a look at the limitations of conventionalSEM’s.

Conventional SEM’s are a mature, well-understood technology. There are manyexcellent texts available that describe them in great detail and the reader is directed tothem for additional information. Here we will limit our discussion to the rudimentaryprinciples prerequisite to an appreciation of the ESEM. This chapter is intendedprimarily for readers with little or no knowledge of SEM’s and may be skipped by otherswithout penalty.

2.1 DESCRIPTION

All SEM’s consist of an electron column, that creates a beam of electrons; a samplechamber, where the electron beam interacts with the sample; detectors, that monitor avariety of signals resulting from the beam-sample interaction; and a viewing system,that constructs an image from the signal.

An electron gun at the top of the column generates the electron beam. In the gun, anelectrostatic field directs electrons, emitted from a very small region on the surface of anelectrode, through a small spot called the crossover. The gun then accelerates theelectrons down the column toward the sample with energies typically ranging from afew hundred to tens of thousands of electron volts. There are several types of electronguns — tungsten, LaB6 (lanthanum hexaboride) and field emission. They use differentelectrode materials and physical principles but all share the common purpose ofgenerating a directed electron beam having stable and sufficient current and the smallestpossible size.

The electrons emerge from the gun as a divergent beam. A series of magnetic lensesand apertures in the column reconverges and focuses the beam into a demagnified imageof the crossover. Near the bottom of the column a set of scan coils deflects the beam in ascanning pattern over the sample surface. The final lens focuses the beam into thesmallest possible spot on the sample surface.


6

The beam exits from the column into the sample chamber. The chamber incorporates astage for manipulating the sample, a door or airlock for inserting and removing thesample, and access ports for mounting various signal detectors and other accessories. Asthe beam electrons penetrate the sample, they give up energy, which is emitted from thesample in a variety of ways. Each emission mode is potentially a signal from which tocreate an image.

2.2 IMAGING PRINCIPLE

Unlike the light in an optical microscope, the electrons in an SEM never form a realimage of the sample. Instead, the SEM constructs a virtual image from the signalsemitted by the sample. It does this by scanning its electron beam line by line through arectangular (raster) pattern on the sample surface. The scan pattern defines the arearepresented in the image. At any instant in time the beam illuminates only a single pointin the pattern. As the beam moves from point to point, the signals it generates vary instrength, reflecting differences in the sample. The output signal is thus a serial datastream. Modern instruments include digital imaging capabilities that convert the analogdata from the detector to a series of numeric values. These values are then manipulatedas desired.

Originally all SEM’s used a simple imaging device based upon a cathode ray tube orCRT. A CRT consists of a vacuum tube covered at one end, the viewing surface, with alight emitting phosphor. At the other end are an electron gun and a set of deflectioncoils. Similar to the SEM, the CRT gun forms a beam of electrons and accelerates ittoward the phosphor. The deflection coils scan the beam in a raster pattern over thedisplay surface. The phosphor converts the energy of the incident electrons into visiblelight. The intensity of the light depends on the current in the CRT electron beam. Bysynchronizing the CRT scan with the SEM scan and modulating the CRT beam currentwith the image signal, the system maps the signal point for point onto the viewingsurface of the CRT, thus creating the image.

MechanicalPump

High VacuumPump

Electron Source

Wehnelt

Anode

Condenser Lenses

Objective Aperture

Scan Coils

Objective Lens

Sample

Display CRT

Magnification Control

Detector

Scan Signals

Image Signal

Sample Chamber

GunChamber

Figure 2-1. Aschematic

representation of anSEM. The electron

column acceleratesand focuses a beam of

electrons onto thesample surface.

Interactions betweenthe sample and the

beam electrons causea variety off signal

emissions. The signalsare detected and

reconstructed into avirtual image

displayed on a CRT.

SEM BASICS

7

2.3 ELECTRON OPTICS

Magnetic lenses in the electron column bend electron paths just as glass lenses bendlight rays. A diverging cone of electrons emerges from each point in the gun crossover,passes through the lens field, and reconverges at a corresponding point in the imageplane of the lens. Electrons from all points in the crossover thus pass through the lens toform an image of the crossover at the image plane of the lens. Since the purpose of thecolumn is to project the smallest possible image of the crossover onto the samplesurface, its lenses operate in a demagnifying mode. In this mode the image plane isalways closer to the lens than the source is. As the cone of electrons converging to apoint in the image passes beyond the image plane it begins to diverge again into anothercone. In a demagnifying configuration, the divergence angle of the cone beyond theimage plane is greater than the divergence angle of the original cone from thecorresponding point in the crossover.

Lenses exhibit certain kinds of aberrations. Two of the most important are sphericalaberration and chromatic aberration. Spherical aberrations result when paths away fromthe optical axis are bent more than paths close the axis. Chromatic aberrations resultwhen paths of slower electrons are bent more strongly than paths of faster electrons.Because of these aberrations, all electron paths originating from a given point in thecrossover do not converge perfectly on the same point in the image.

Apertures are simply small holes, centered on the optical axis, through which the beammust pass. Located at an image plane, an aperture limits the size of the image. Locatedat a lens plane, an

Figure 2-2. Theinteractions of beamelectrons and sampleatoms generate avariety of signals. Themost commonly usedsignals are secondaryelectrons,backscatteredelectrons, andcharacteristic X-rays.

Cathodoluminescence(light)

Auger electrons

Backscattered electrons

Characteristic X-rays

Bremsstrahlung

Secondary electrons

Primary beam

Heat

Elastically scattered electronsTransmitted electrons

Specimen current

X-rays

2.3.1 Lenses

2.3.2 Apertures


8

aperture defines the base of the cone of electrons passed from each point in the image,and, thus, the number of electrons transmitted. Here it operates more or less equally onall points in the image of the crossover, and limits total current in the beam. Equallyimportant, an aperture in the lens plane excludes the electrons that are farthest off axis,reducing the adverse effects of lens aberrations. For any beam current there is anoptimal aperture size that minimizes the detrimental effects of lens aberrations on spotsize. As the beam passes from lens to lens in the column, apertures eliminate the morewidely diverging electrons, sacrificing beam current for smaller spot size.

There is a fundamental relationship between beam current and spot size. An increase inone generally increases the other. Larger apertures and weaker lenses yield higher beamcurrents and larger spot sizes. Smaller apertures and stronger lenses yield smaller beamcurrents with smaller spot sizes. Some applications, for instance X-ray analysis, needhigher current. High resolution imaging, on the other hand, requires the smallestpossible spot size.

Beam current requirements ultimately impose a lower limit on spot size. Theinformation in an SEM image consists of variations in signal intensity over time. Atlower beam currents, random variations in the signal become increasingly significant.This noise may originate in the detection and amplification chain or, at very lowcurrents, in statistical fluctuations of the beam current itself. As beam current and spotsize decrease below some critical level, increasing noise overwhelms improvingresolution.

For the purposes of this discussion, we must also distinguish between beam currentand imaging current. We will call beam current the current that passes through the lastaperture of the electron column. Imaging current is the current remaining in the spot atthe sample surface. Imaging current is less than beam current when gas molecules in thesample environment scatter electrons out of the beam. In the high vacuum environmentof a conventional SEM beam current and imaging current are essentially the same.

Figure 2-3. The finalaperture limits beamcurrent and reduces

the effects of lensaberrations. For any

set of lens conditions,there is an aperture

size that optimizes thetrade off between

beam current and spotsize. Larger beam

currents requirelarger apertures.

2.3.3 Beam Current

Electron Source(Crossover)

Condenser Lens

Objective Lens Aperture

Image of Source

Sample

Image of Source

Divergence

IncreasedExcluded by Aperture

(further demagnified)

(demagnified)

Divergence

Chromatic Aberration Spherical Aberration

Minimum Spot Size

Slower electronsfocus closerto lens

wider anglesElectrons at

focus closerto lens

Column Optics Lens Aberrations

SEM BASICS

9

2.4 RESOLUTION

Resolution is a measure of the smallest feature a microscope can “see”. It defines thelimit beyond which the microscope cannot distinguish two very small adjacent pointsfrom a single point. Resolution is specified in linear units, typically Angstroms ornanometers. Just to keep things interesting, better resolution is called higher resolution,even though it is specified by a lower number. For example 10Å is higher (better)resolution than 20Å.

The size of the spot formed by the beam on the sample surface sets a fundamental limiton resolution. An SEM cannot resolve features smaller than the spot size. In general,low beam current, short working distance and high accelerating voltage yield thesmallest spot. Other factors such as type of signal, beam penetration, and samplecomposition also affect resolution.

Image signals are not generated only at the sample surface. The beam electronspenetrate some distance into the sample and can interact one or more times anywherealong their paths. The region within the sample from which signals originate andsubsequently escape to be detected is called the volume of interaction. Signal type,sample composition, and accelerating voltage all impact resolution through their effectson the size and shape of this volume. Figure 2-5 is a schematic representation of thetypes of signals generated and their specific volumes of interaction. In most cases thevolume of interaction is significantly larger than the spot size and thus becomes theactual limit on resolution.

Accelerating voltage determines the amount of energy carried by the primary (beam)electrons. It affects the size and shape of the volume of interaction in several ways.Higher energy electrons can penetrate more deeply into the sample. Likewise, they cangenerate higher energy signals that can escape from deeper within the sample. Primaryelectron energy is also a factor in determining the probability that any particular type ofinteraction will occur. In all of these instances higher energy tends to reduce imageresolution by enlarging the volume of interaction. Higher accelerating voltage can alsoimprove resolution by reducing lens aberrations in the electron column, resulting insmaller spot sizes. Which influence predominates depends upon the specific sample,operating conditions, and signal type.

ConvergenceAngle

Spot Diameter

Figure 2-4. Resolutionis fundamentally

limited by thediameter of the spot

formed by the electronbeam on the sample

surface. Theconvergence angle

determines depth offield.

2.4.1 Spot Size

2.4.2 Volume of

Interaction

Accelerating Voltage


10

Sample composition affects both the depth and shape of the volume of interaction.Denser samples reduce beam penetration and reduce the distance a signal can travelbefore it is reabsorbed. The resulting volume of interaction tends to be shallower andmore hemispherically shaped.

To this point we have discussed a general volume of interaction from which all signalsoriginate. We can divide that volume into specific regions associated with each signaltype.

Secondary electrons (SE) are sample atom electrons that have been ejected byinteractions with the primary electrons of the beam. They generally have very lowenergy (by convention less than fifty electron volts). Because of their low energy theycan escape only from a very shallow region at the sample surface. As a result they offerthe best imaging resolution. Contrast in a secondary electron image comes primarilyfrom sample topography. More of the volume of interaction is close to the samplesurface, and therefore more secondary electrons can escape, for a point at the top of apeak than for a point at the bottom of a valley. Peaks are bright. Valleys are dark. Thismakes the interpretation of secondary images very intuitive. They look just like thecorresponding visual image would look.

Backscattered electrons (BSE) are primarily beam electrons that have been scatteredback out of the sample by elastic collisions with the nuclei of sample atoms. They havehigh energy, ranging (by convention) from fifty electron volts up to the acceleratingvoltage of the beam. Their higher energy results in a larger specific volume ofinteraction and degrades the resolution of backscattered electron images. Contrast inbackscattered images comes primarily from point to point differences in the averageatomic number of the sample. High atomic number nuclei backscatter more electronsand create bright areas in the image. Backscattered images are not as easy to interpretbut, properly interpreted, can provide important information about sample composition.

Sample Composition

2.4.3 Signal Type

Figure 2-5. Each typeof signal originateswithin a specificvolume of interaction.The size of the volumelimits the spatialresolution of thesignal. Secondaryelectrons have thesmallest volume,followed bybackscatteredelectrons, and X-rays.

backscattered electrons

Source of

Source of

Source of

electron-excited

characteristic X-rays

Primary electron beam

Sample secondary electrons

Secondary Electrons

BackscatteredElectrons

SEM BASICS

11

Figure 2-6. Secondaryelectron (left) and

backscattered electron(right) images of goldon carbon. Gold is a

heavy element,providing great atomic

number contrast withthe carbon

background. This typeof sample tends to

minimize thedifferences in SE and

BSE resolution.

Figure 2-7. Thissample shows light

element particles ona tungsten carbidesubstrate. The SEimage (left) shows

mostly topographiccontrast. Note the

surface detail of theparticles. Contrast in

the BSE image(right) is dueprimarily to

differences in atomicnumber.

Figure 2-8.Secondary electron

(left) andbackscattered

electron (right)images of toner

particles. A lightelement matrix, such

as this, emphasizesthe resolution

differences.


12

2.5 DEPTH OF FIELD

Compared to light microscopes, SEM’s offer a great improvement in depth of field.Depth of field characterizes the extent to which image resolution degrades with distanceabove or below the plane of best focus. With greater depth of field a microscope canbetter image three dimensional samples. Although the SEM is best known for itsexcellent resolution, some of the most dramatic images actually result from itstremendous depth of field.

In a light microscope, the divergence angle of the cone of light collected by theobjective lens from each point in the sample determines depth of field. For highermagnifications, this angle is greater and the depth of field shallower. Thus there is adirect trade-off between magnification and depth of field.

The SEM largely decouples magnification from depth of field. The size of the beamscan, relative to the display scan, determines magnification. The convergence angle ofthe primary beam determines the change in spot size with distance above or below theplane of best focus. Although the convergence angle and spot size are a function ofworking distance (the distance from the final lens to the sample surface), in all cases theangles are much smaller, and depth of field much greater, than for optical microscopies.

2.6 MICROANALYSIS

X-rays result when an energetic electron, usually from the beam, scatters an inner shellelectron from a sample atom. When a higher energy, outer shell electron of the sameatom, fills the vacancy, it releases energy as an X-ray photon. Because the energydifferences between shells are well defined and specific to each element, the energy ofthe X-ray is characteristic of the emitting atom.

An X-ray spectrometer collects the characteristic X-rays. The spectrometer countsand sorts the X-rays, usually on the basis of energy (Energy Dispersive Spectrometry —EDS). The resulting spectrum plots number of X-rays, on the vertical axis, versusenergy, on the horizontal axis. Peaks on the spectrum correspond to elements present inthe sample. The energy level of the peak indicates which element. The number of countsin the peak indicates something about the element’s concentration.

Electron Beam

Plane of Best

Sample surface

Region in Effective Focus

Focus

Depth of Field

Figure 2-9. The SEMlargely decouples

depth of field frommagnification. Often

the dramatic impact ofan SEM micrograph is

due more to depth offield than resolution.

CharacteristicX-rays

SEM BASICS

13

Most elements have multiple energy shells and may emit X-rays of several differentenergies. The various emission “lines” are named for the shell of the initial vacancy —K, L, M, etc. A Greek letter subscript indicates the shell of the electron that fills thevacancy. Thus a Ka line results from a vacancy in the K shell filled by an electron fromthe next higher shell, L in this case. The nomenclature and the peak structures canbecome very complex, particularly for high atomic number elements with a multitude ofshell and sub-shell energy levels.

Some general rules apply to the various spectral lines. 1) For a given element, lowerline series have higher energy — gold K lines have higher energy than gold L lines. 2)Within a line series, higher atomic number elements emit higher energy X-rays —oxygen K lines are higher energy than carbon K lines. 3) Lower line series have simplerstructure than higher line series. K lines are simple and distinct. L and M lines, becomeprogressively more complex and overlapping.

For a number of reasons, the X-ray signal provides a much poorer image than electronsignals. One reason is the distance X-rays can travel through the sample, generating alarge volume of interaction and poor spatial resolution (see Figure 2-5). Another reasonis the inherent X-ray background signal (Bremsstrahlung) that, combined withintrinsically low characteristic X-ray signal levels, yields a poor signal to noise ratio.

X-ray Lines

Figure 2-10.Characteristic X-rays

are generated when aninner shell vacancy is

filled by a higherenergy outer shell

electron. The energyof the X-ray equals thedifference between theelectron energies and

is characteristic of theemitting element.

Inner Shell

ElectronPrimary

Electron

OuterShellElectron

X-rayPhoton

M

Line

Lines

L

KLines

αβ

α

α

β

γ

X-ray Maps

Figure 2-11. Anenergy dispersive X-ray spectrometerdisplays peaks atenergies characteristicof elements present inthe sample.


14

X-ray images are generally referred to as maps, rather than images. Setting thespectrometer to register a “dot” on the imaging device when it detects an X-ray of theappropriate energy creates a “dot map”, showing the spatial distribution of thecorresponding element. Given sufficiently long collection times, the digital imagingcapabilities of current generation EDS systems can generate gray level maps that showrelative X-ray intensity at each point (Figure 2-12). Even a gray level map does notapproach the quality of an electron image.

Because of its poor spatial resolution, the X-ray signal is more often used for analysisthan imaging. A qualitative analysis seeks to determine the presence or absence ofelements in the sample based on the presence or absence of their characteristic peaks inthe spectrum. A quantitative analysis tries to derive the relative abundance of theelements in the sample from a comparison of their corresponding peak intensities, toeach other, or to standards. The many interactions that may occur between characteristicX-rays and sample atoms make quantitative analysis very complex.

2.7 WHY AN ESEM ? — SEM LIMITATIONS

Although conventional SEM’s have superior resolution, depth of field, andmicroanalytic capabilities, they also have a number of limitations. Almost all of theselimitations derive from the high vacuum a CSEM must maintain in its sample chamber.

That CSEM’s developed as high vacuum systems is probably due more to the historicalcontext of their development than to strict technical requirements. The column requireda high vacuum in order to generate and focus the electron beam. The sample chamberrequired a high vacuum to permit the use of available secondary electron detectors. Thesimplest design, then, was to allow the chamber and the column to share a common highvacuum environment. At the time, the penalties paid for this approach must haveseemed small compared to the performance benefits.

Figure 2-12. X-raymaps plot the locationand intensity ofcharacteristic X-rayemissions over thefield of view. Theseimages show(clockwise from upperleft) a secondaryelectron image, anoxygen map, amagnesium map, andan aluminum map.

X-ray Analysis

2.7.1 SEM Vacuum

Constraints

SEM BASICS

15

All electron guns, regardless of type, are very sensitive to vacuum levels. Gas in the gunchamber can interfere with electron emission and degrade or destroy the electron source,be it tungsten, LaB6 or field emission. Moreover, the gun uses very high voltages toaccelerate the electrons down the column. The fields generated by these voltages arestrong enough to ionize any gas present, providing a path for electrical discharge or“arcing”.

Gas in the column can also interfere with the formation and transmission of thebeam. Since the focal lengths of the magnetic lenses are relatively long, the beamelectrons must travel a considerable distance (typically tens of centimeters) from the gunto the sample. Gas molecules along the beam path can scatter the electrons and degradecolumn performance.

The secondary electron detector used in most conventional SEM’s is known as anEverhart-Thornley (ET) detector, named for its inventors. Like other secondary electrondetectors, it uses a positive bias of a few hundred volts to attract the low energysecondary electrons and increase its collection efficiency. The detector field has littleeffect on higher energy backscattered electrons. Having entered the detector through thecollector grid, secondary electrons are immediately accelerated by a higher voltage field(ten to twelve thousand volts) toward a scintillator. The scintillator converts the electronsignal to light, which then passes through a light pipe to a photomultiplier tube. Thephotomultiplier tube amplifies the light signal and converts it back to an electronicsignal. An electronic amplifier further amplifies and conditions the signal before passingit along to the imaging system. Because of its exposed high voltage elements, an ETdetector can only function in a high vacuum environment. In a gas environment, it toowill arc, often damaging or destroying itself in the process.

What constraints does the high vacuum requirement impose on samples? In the simplestterms, CSEM’s require that samples be vacuum tolerant, vacuum friendly andelectrically conductive.

Vacuum tolerant means that the sample is not changed by the high vacuum environmentof the sample chamber. A piece of metal is, generally, vacuum tolerant. A volatilecoating on that same piece of metal is not. A delicate biological structure, perhapssupported by internal hydrostatic forces, is not. Much of specimen preparation for theCSEM involves the substitution of non-volatile materials for volatile samplecomponents. Accomplishing this without altering the sample is difficult at best. CSEMsample preparation and analysis has been called “the art of creative artifact.” Thescience lies in correctly interpreting the observed artifact.

Gun Chamber andColumn

Wehnelt

Cathode voltage (e.g. -30 kV)

Wehnelt voltage(e.g -30.5 kV)

Anode (0 V)

Electron "crossover"

electrons

Filament

Electron Beam

Collector grid

Scintillator

Light guide

Photo-multiplier

Secondary electrons

(+300 V)

(+12 kV)

SecondaryElectronSignal Out

ET Detector

Figure 2-13. The highvoltages used in the

electron gun andEverhart-Thornleysecondary electrondetector require a

high vacuumenvironment.

2.7.2 Sample Constraints

Vacuum Tolerant


16

Vacuum friendly is really the opposite perspective on vacuum tolerant. Vacuum friendlydescribes the impact of the sample on the instrument. Will the sample degrade thevacuum enough to damage the detector or electron gun? Will it leave deposits on theapertures of the electron column, degrading imaging performance? Will it leavesufficient contamination on the walls of the sample chamber to interfere with subsequentobservations?

The connection between electrical conductivity and sample chamber vacuumrequirements is less obvious. The electron beam deposits considerable charge in thesample. In conductive materials, the charge flows through the sample stage to ground.In insulating materials, the charge accumulates, causing local variations in secondaryelectron emissions and, in extreme cases, deflecting the electron beam itself. All of theseeffects are classified as charging artifacts.

Techniques for eliminating charging artifacts on nonconductive samples fallgenerally into two categories: conductive coatings, and low voltage charge balancing.Applying a thin conductive coating to the sample provides a path to ground anddissipates the local fields caused by accumulating charge. A heavy element coating, suchas gold, may also improve signal strength and apparent resolution. As with any samplepreparation, coating raises the issue of preparation artifacts. Does the coating processitself significantly alter the sample? Moreover, an image of a gold coated sample is animage of the coating not the sample. Are they the same?

Coatings may interfere in other ways. For example, a gold coating renders invisiblethe gold particles sometimes used as labels. In microanalysis, sample X-rays may beabsorbed by the coating or obscured by coating X-rays. Gold absorbs X-rays veryefficiently and emits interfering X-rays at several energies. Even carbon, a light elementcoating, can cause unacceptable interference.

Low voltage charge balancing works by balancing the charge deposited in the sampleby the electron beam against the charge emitted from the sample as various signals. Thebalance is a function of accelerating voltage, sample composition, and local topography.Charge balancing generally requires accelerating voltages between a few hundred andtwo thousand volts, exacting a penalty in spot size and, potentially, in resolution.Furthermore, since the balance is specific to local composition and topography, it maybe difficult to achieve simultaneously over the entire field of view. Finally, low voltagescomplicate X-ray analysis by requiring the use of more complex L and M lines.

Vacuum Friendly

ElectricallyConductive

Figure 2-14. Left - Inhigh vacuum, at 20

kV, charging artifactsare apparent on this

insulating sample.Right - Even low

accelerating voltage(1.7 kV) may not

eliminate charginguniformly over the

entire field of view.

SEM BASICS

17

2.8 SUMMARY

SEM’s offer superior performance compared to light microscopes, particularly inresolution, depth of field, and microanalysis. An SEM can form an image from a varietyof signals. Of the most commonly used signals, secondary electrons offer the bestresolution and carry information about surface topography. X-rays carry the bestinformation about sample composition but have poor spatial resolution. Backscatteredelectrons occupy the middle ground offering a medium resolution image carryingsignificant but non-specific compositional information.

Though SEM’s offer superior performance, they are limited by their high vacuumrequirements to samples that are vacuum tolerant, vacuum friendly and electricallyconductive. Certainly the number of applications that do not meet these criteria must farexceed the number that do. In some cases, sample preparations can extend theconventional SEM’s application. Even when successful, these techniques are expensiveand time consuming. More importantly, they unavoidably call into question the integrityof the information derived from the modified sample. What does it look like in itsnatural state?

18

3 THE ESEM

The previous chapter ended with a question, “What does it look like in its natural state?"It was exactly this question that led to the development of the Environmental ScanningElectron Microscope. Researchers in Australia wanted to look at wool in its natural state— wet, oily and dirty — definitely vacuum intolerant, very vacuum unfriendly andhighly non-conductive. They realized that the solution lay in eliminating the highvacuum requirement in the sample chamber. To do this they had to cross two technicalhurdles. First they had to separate the vacuum environment of the electron column fromthe environment of the sample chamber. Second, they needed a secondary electrondetector that could function in this non-vacuum sample environment. Their solutions tothese problems are the keys to the development of the Environmental SEM.

3.1 VACUUM SYSTEM

All SEM’s require high vacuum conditions in the electron gun, where high voltages areused to generate and accelerate the electron beam. High vacuum is also desirablethroughout the column, where gas molecules can scatter electrons and degrade thebeam. In the ESEM, multiple Pressure Limiting Apertures (PLA’s) separate the samplechamber from the column. The column remains at high vacuum while the chamber maysustain pressures as high as 50 Torr.

The balance of gas flows into and out of the ESEM sample chamber determines itspressure. Gas flows out of the sample chamber to the column through the pressurelimiting apertures, at a rate determined by each aperture’s size and the pressuredifferential across it. Gas flows into the chamber from a selected source through anautomatic metering valve controlled by the operator. Changing the inflow rate changesthe vacuum level in the chamber. The environmental gas admitted to the chamber maybe inert or may comprise one of the reactants in the experimental system. The choice ofgases is limited primarily by practical considerations such as toxicity, flammability, andchemical reactivity with components of the chamber and vacuum system.

Prior to the ESEM some work was done using a single PLA to separate the samplechamber from the column, but conflicting optical and vacuum requirements — anaperture large enough to pass the beam but small enough to limit gas flow — permittedonly limited benefits.

THE ESEM

19

The essential breakthrough in the design of the ESEM vacuum system was theintegration of two closely spaced pressure limiting apertures into the final lens of theelectron column. The regions below, between, and above the PLA’s are separatelypumped to provide a graduated vacuum from as low as 50 Torr, in the sample chamber,to 10-5 Torr, or better, in the column and gun. Depending on the particularconfiguration, additional pumping stages may be added to further improve vacuum inthe gun. By using multiple apertures, the designers were able to decrease the pressuredifferential across each aperture and use larger aperture diameters, while still achievinga large total pressure difference between the column and the sample chamber. Bylocating the apertures close together at the bottom of the column they reduced thedistance the beam has to

Sample Chamber

GunChamber

High VacuumPump

MechanicalPump

10 Torr-5

Figure 3-1. In aCSEM the column andspecimen chambershare the samevacuum.

Manual Valve

G4

G1 G2V2

V5G3 V4

V3

V13G5 V7

V8

Regulator Valve

V10

V9

V11

Auxiliary Gas

Vent

V6

G7

Dif 1

Dif 2

RP1

RP2

RP3

V1 V12

Vent

Water Vapor

Gauge

ValveIon

Pump

Sample Chamber10 Torr

EC110 Torr-1

EC210 Torr-4

Column10 Torr-5

GunChamber10 Torr-7

Figure 3-2. In theESEM the vacuumsystem is divided intoas many as five stagesof increasing vacuum,separated by pressurelimiting apertures. Inthis schematic thestages are the samplechamber, firstenvironmentalchamber (EC1),second environmentalchamber (EC2),column, and gunchamber.

3.1.1 Multiple Pressure

Limiting Apertures


20

travel through thehigher pressure stages. This type of vacuum system is protected by multiple patents andis available only in the ESEM.

If resolution in an SEM depends on its ability to focus the beam electrons into thesmallest possible spot on the sample surface, how can the ESEM maintain itsperformance in a gaseous environment? Does the gas not scatter the primary electronsand degrade resolution? Yes, and no. Yes, the gas scatters electrons. No, it does notnecessarily impact resolution. In order to understand the effects of the gas on the beamwe must look more closely at electron scattering.

Although scattering may occur anywhere along the beam path from gun to sample,apertures in the column prevent most electrons scattered there from ever reaching thesample. Most scattering that could affect resolution occurs between the final pressurelimiting aperture at the bottom of the column and the sample surface, hence the need toreduce this distance to a minimum.

It is of the utmost importance to understand that scattering is a discrete process, nota continuous one. Each individual electron is deflected only when it passes within acertain critical distance of a gas molecule. Otherwise, it continues on its originaltrajectory. Thus each electron has a finite, integer number of collisions before it reachesthe sample surface. There is a statistical distribution that describes this kind of process,called a Poisson distribution. According to this distribution, the fraction of electrons thatfalls into each number-of-collisions category depends only on the average number ofcollisions for all electrons. Most importantly, even when the average number ofcollisions per electron is large, some small fraction of electrons still falls into the zero-collisions category.

The average number of collisions (m) provides a basis for defining three differentscattering regimes. For the Minimal Scattering Regime, the average ranges from 0 to0.05. At the upper limit (m = 0.05) 95% of the electrons in the beam have no collisions.Conventional SEM’s operate in the lower portion of this range (m ® 0) where scatteringeffects on the beam are insignificant.

At the other end of the spectrum is the Complete Scattering Regime. Here theaverage number of scattering events per electron is greater than 3 and 95% or more ofthe electrons are scattered at least once. In this range the beam is generally broadenedand not useful for SEM imaging.

3.1.2 Beam-Gas

Interactions

PLA 1 PLA 2

10 Torr10 Torr-110 Torr-410 Torr-5

Figure 3-3. TwoPressure LimitingApertures (PLA’s)integrated into thefinal lens assemblypermit vacuums as lowas 50 Torr in thesample chamber whilemaintaining highvacuum conditions inthe gun. Keeping theapertures closetogether at the bottomof the columnminimizes the effectsof electron scattering.

THE ESEM

21

Between Minimal Scattering and Complete Scattering is the Partial ScatteringRegime. Here the average number of scattering events ranges from 0.05 to 3. Over thisrange, 95% to 5% (respectively) of electrons pass without scattering. This fact carriesprofound implications for imaging in the ESEM.

In a Poisson Process, events occur randomly over a continuum of time or space. Thescattering of electrons by gas molecules is such a process. In a Poisson Distribution, theprobability that any number of events will occur within a specified interval is a functiononly of the mean of the distribution. For electron scattering, the parameter of interest isthe number of collisions each electron has with gas molecules along its path. Theinterval is the distance the electron travels through the gas. The mean of the distributionis the average number of collisions per electron, for all electrons.

The Poisson Distribution is described mathematically as:

P(x) = mxe-m/x!

where: P(x) is the probability an electron will scatter x timesm is the average number of scattering events per electrone is the base of natural logarithms, 2.71828...

For x=0, the probability that an electron will not scatter at all, the equation reducesto:

P(0) = e-m

Minimal ScatteringScatter < 5%

m < 0.05

Partial Scattering5% to 95% Scatter

m from = 0.05 to 3.0

Complete ScatteringScatter >95%

m > 3.0

Figure 3-4. It is usefulto define three

scattering regimesbased on the averagenumber of scattering

events per electron, m.Conventional SEM’s

operate in the MinimalScattering Regime.

ESEM’s and LV-CSEM’s operate in the

Partial ScatteringRegime. The Complete

Scattering Regime isnot used for SEM

imaging.

Aside: A Little Statistics (Very Little)


22

It seems reasonable to expect the electron beam to broaden gradually, but maintain itsGaussian profile, with increasing gas pressure. This, in fact, does not happen. Instead,the spot loses current without broadening, until it eventually disappears below thebackground.

Think of the beam as divided into two components, scattered and unscattered. Theunscattered component remains well focused in the original spot on the sample surface.The scattered component, called the beam “skirt”, falls in some broader distribution.The overall intensity profile of the beam is the sum of the two component profiles. Theintensity of the skirt relative to the intensity of the spot determines the degree to whichthe skirt interferes with imaging.

Limited experimental data suggest the following relationship for the skirt half radius(r1/2), the radius encompassing half of the scattered electrons:

r1/2 = 0.0039 d + 1.326 d(pd)1.38

For typical ESEM conditions (d = 0.002 m, p = 7.5 Torr) the skirt half radius isabout 16 micrometers. This is tremendously larger than the spot half radius of a fewnanometers. Even at the upper limit of the partial scattering regime, the 5% of electronsnot scattered are concentrated in an area many orders of magnitude smaller than thearea of the skirt. As a result, the skirt electrons contribute only a very low levelbackground signal that is easily discarded. As long as current sufficient to form animage remains in the spot, image resolution is unaffected.

3.1.3 Imaging Resolution

Average Number ofScattering Events = 0.05

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10

Number of Scattering Events%

Pro

babi

lity

Average Number ofScattering Events = 0.7

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10

Number of Scattering Events

% P

roba

bilit

y

Average Number ofScattering Events = 3

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10

Number of Scattering Events

% P

roba

bilit

y

Figure 3-5. A Poissondistribution is

determined entirely byits mean. At the lower

limit of the PartialScattering Regime,

95% of electrons donot scatter. At the

upper limit, only 5%do not scatter.

Minimal Scattering Regime Partial Scattering Regime Complete Scattering Regime

Figure 3-6. The shapeof the beam intensity

profile depends on thescattering regime. As

scattering increasesthe beam loses current

to a very broadlydispersed “skirt”. The

unscatteredcomponent loses

intensity but does notbroaden, remaining

within the originalspot on the sample

surface.

THE ESEM

23

Imaging in a gaseous environment is thus limited by the useful current remaining in theunscattered beam spot, not by beam spreading. How does the statistical parameter m, theaverage number of scattering events per electron, relate to the operational parametersthe microscopist can control, such as pressure and working distance? What is theESEM’s useful operational range?

Intuitively, m should depend on the number of gas molecules per unit volume (n), theeffective size of the molecules (s) and the distance the electron travels through the gas (din meters, also called Beam Gas Path Length or BGPL).

For known temperature (T in °K)and pressure (p in Torr), the ideal gas law gives nas:

n = 9.655 X 1024 p/T

In the energy range of beam electrons, the angular deflection and energy loss foreach scattering event are relatively small. Therefore, for m less than three, the pathlength through the gas, d, very nearly equals the straight line distance from the finalPLA to the sample surface. Working distance is usually defined as the distance from thebottom of the final lens to the sample surface. In the ESEM the final PLA extends belowthe bottom of the final lens so the path length is less than the working distance by somefixed amount.

The effective size, s, of a molecule is called its scattering cross section. A detaileddiscussion of the determination of scattering cross sections is beyond the scope of thiswork. Both theoretical derivations and experimental

3.1.4 Imaging Current

Figure 3-7. As thesemicrographs

demonstrate, there isno inherent loss of

resolution in agaseous environment.

Upper Left - Magnetictape at 50,000 X in 8.4

Torr of water vapor.Upper right -

Magnetic tape at50,000 X in high

vacuum. Lower left -Toner particles at

30,000 X in 5.4 Torrof water vapor. Lowerright - Toner particles

at 30,000X in highvacuum.


24

measurements are available. It is sufficient here to note that scattering cross sectionis specific to each type of gas molecule, and that it varies inversely with the energy ofthe beam electron (V) — higher energy electrons are less likely to scatter.

It can be shown that, in the Partial Scattering Regime, the average number ofcollisions per electron is given by:

m = s n d

Combining this with the previous equations for n and P(0), and collecting theconstants with scattering cross section into a single constant (k) specific to gas type, wecan derive an equation for the fraction of electrons not scattered:

I(0) / ITotal = e-kpd/TV

The table below shows this fraction, as a percentage, for water vapor at variouspressures under typical ESEM operating conditions.

Imaging Current - Room Temperature, Water Vapor, 20 kVPressure % of Primary Beam Current

Torr Pascals ESEM - BGPL = 2 mm40 5320 5%20 2660 23%10 1330 48%7 931 60%5 665 69%2 266 86%1 133 93%

0.5 66.5 96%

Beam Loss due to gas dispersion (at 20kV)

1%

10%

100%

0 5 10 15 20 25 30

Path length from Pressure Limiting Aperture to the sample (mm)

Use

ful I

mag

ing

Bea

m C

urr

ent

50%

10 Torr

5 Torr

2 Torr

1 Torr

0.5 Torr

0.2 Torr

Figure 3-8. Plots thepercentage of useful

imaging current(unscattered electrons

remaining in theoriginal spot) for

various combinationsof gas path length and

sample chamberpressure. In this

example the gas iswater vapor, and the

accelerating voltage is20 kV.

THE ESEM

25

3.2 ENVIRONMENTAL SECONDARY DETECTORS

Secondary electrons provide the highest resolution images. Unfortunately, the Everhart-Thornley (ET) detector used in the CSEM cannot function in the gaseous environmentof the ESEM. In its place the ESEM uses a proprietary Environmental SecondaryDetector (ESD). The most recent generation of the ESD, the Gaseous SecondaryElectron Detector (GSED), provides better discrimination against parasitic electronsignals. Both ESD and GSED are patented and available only in the ESEM

In its simplest form the ESD is a conical electrode, about a centimeter in diameter,positioned apex down, concentric with the beam, at the bottom of the pole piece. Thebeam passes through the detector, exiting from the integrated final pressure limitingaperture. The detector’s location directly above the sample eliminates the need to tilt thesample for improved detector efficiency

A positive potential of a few hundred volts, applied to the detector, attracts secondaryelectrons emitted by the sample. As the electrons accelerate in the detector field theycollide with gas molecules. The resulting ionizations create additional electrons, calledenvironmental secondary electrons, and positive ions. This process of acceleration andionization repeats many times resulting in a proportional cascade amplification of theoriginal secondary electron signal. The detector collects this signal and passes it directlyto an electronic amplifier.

The ionization characteristics of the gas in the sample chamber affect the imagingprocess directly. The more easily the gas ionizes, the higher the amplification gain willbe. Varying the detector bias modulates the gain and permits the use of a variety ofdifferent gases. The most commonly used environmental gas is water vapor. It ionizeseasily to provide excellent imaging performance. It is convenient and non-toxic. Last butnot least, it is an abundant component of our own environment and, thus, frequently ofinterest as part of the experimental system under observation.

Because the ESD does not use a photomultiplier tube it is insensitive to light. Lightfrom the sample, for example, incandescence from heated samples,cathodoluminescence, or fluorescence, does not interfere with imaging. Likewise, thedetector permits the use of the chamber viewport or an integrated optical microscope,with illumination, during image acquisition.

3.2.1 ESD

V

+

Vout

A

Gas Molecules

Positive Ions

Electrons

Figure 3-9. TheEnvironmentalSecondary Detectoruses gas ionization toamplify the secondaryelectron signal. Innonconductivesamples, positive ionsare attracted to thesample surface ascharge accumulatesfrom the beam. Therethey effectivelysuppress chargingartifacts.


26

The Gaseous Secondary Electron Detector (GSED) is a refinement of the original ESD.It improves image quality by discriminating against spurious signals from backscatteredelectrons and type III secondary electrons.

All secondary electron detectors, conventional or environmental, are also sensitive tobackscattered electrons (BSE). Backscattered electrons have an angular emissiondistribution with a maximum normal to the sample surface. Conventional detectors aretypically located to the side of and some distance away from the sample. This reducesthe number of BSE’s that reach them. Because the ESD is directly above and very closeto the sample, it collects more backscattered electrons than conventional secondarydetectors. The backscattered contribution degrades the contrast and resolution of thesecondary electron signal.

Secondary electrons (SE) are classified into three types based on their origin. Type Isecondary electrons result from interactions between beam electrons and sample atoms,and escape only from a very shallow region where the beam enters the sample. These arethe secondaries that carry high resolution image information. Type II secondaryelectrons result from interactions between sample atoms and backscattered electrons asthe backscattered electrons exit through the sample surface. Since BSE’s may travel aconsiderable distance through the sample before escaping, type II SE’s have relativelypoor resolution. Type III secondary electrons occur when a backscattered electroncollides with the walls of the sample chamber or some other component of themicroscope. They generally follow the intensity and resolution of the backscatteredsignal.

The GSED occupies the same physical location as the ESD (see figure 3-10). It isfabricated as a printed circuit board. A seal on the back side joins a housing screwedinto the pole piece and vacuum manifold of the ESEM. The final PLA is

BSE

Type III SE

SE

Objective Lens

Insulator

High VoltageCollection Electrode

PLA1

Gas Tight Seal

SE

BSE

Type III SE

BSESuppressor Electrode

Suppressor Electrode

Detector Ring

ESD

GSED

SE

SE

Figure 3-10. TheGaseous SecondaryElectron Detector(GSED) discriminatesagainst backscatteredelectrons and parasiticType III secondaryelectrons to improveimage quality andapparent resolution.

3.2.2 GSED

BSE’s

Type I, II, III SE’s

BSE Discrimination

THE ESEM

27

integrated into the printed circuit board. The suppressor electrode covers the lowersurface of the assembly and is in physical and electrical contact with the PLA. Thedetector ring is suspended below and parallel to the suppressor electrode. The electrodeand the detector ring are biased to shape the detector field. Low energy SE’s will followpaths influenced by the shape of this field. Since the ring is closer to the sample than thesuppressor, it creates a stronger field and attracts a larger share of SE’s than its apparentrelative area represents.

BSE’s impacting the suppressor electrode have the potential to create Type III electrons.Since the suppressor is positively biased, type III’s created there are unable to escape tothe detector ring. Because of its size and position, the suppressor electrode also preventsmost type III’s generated elsewhere in the sample chamber from reaching the detectorring.

The original ESD did not isolate the pressure limiting aperture from the detectorelectrode. BSE’s passing through the PLA can create type III’s within the pole piece andfirst environmental chamber. The back side of the ESD detector electrode collects thesetype III’s. The GSED separates the PLA from the detector ring. The PLA and suppressorelectrode shield the detector ring from Type III’s generated within the pole piece.

The GSED’s ability to discriminate against type III secondary electrons andbackscattered electrons significantly enhances the quality and apparent resolution ofimages from the ESEM. Figure 3-11 compares images taken with the ESD and GSEDdetectors.

One of the greatest benefits of the ESEM is the absence of charging artifacts. Chargingartifacts occur in conventional SEM’s when charge deposited by the beam accumulatesin insulating samples. The fields induced by charging cause local variations insecondary electron emissions, and deflections of the primary beam. Both interfere withimaging. In the ESEM, positive ions, generated by the signal amplification process, areattracted to the sample surface as charge accumulates. There, they suppress the localfields and effectively eliminate charging artifacts (See Figure 3-9).

Charge suppression in the ESEM permits the imaging of nonconductive samples intheir natural, uncoated state. The mechanism operates at all accelerating voltages,freeing the microscopist to manipulate beam energy for purposes other than chargebalance. It permits simultaneous imaging and X-ray

Type III SEDiscrimination

Figure 3-11. Left -ESD image of toner

particles. Right -GSED image of the

same sample. Note theenhanced edge effects,

indicative of theincreased secondary

electron contributionto the image signal.

3.2.3 Charge Suppression


28

analysis using less complex, higher energy K-lines. It is self-adjusting, suppressingcharge as and where it occurs across the image field.

3.3 X-RAY ANALYSIS IN THE ESEM

The lack of charging artifacts in the ESEM has direct benefits for X-ray analysis. Iteliminates the interference of sample coatings and it permits analysis at higheraccelerating voltages on non-conductive samples. However there are additional variablesto be considered in optimizing the ESEM for X-ray analysis.

Any coating applied to a sample contributes to the characteristic X-ray spectrum. X-raysfrom the coating can interfere with the detection and counting of X-rays from sampleelements having lines of the same energy. For instance, gold, a commonly appliedconductive coating, has M lines at the same energy as the K-lines of sulfur. Coatingsalso absorb X-rays generated in the sample. Gold, being a heavy element, is alsoparticularly good at absorbing X-rays. The absence of conductive coatings on ESEMsamples eliminates the potential for absorption and interference.

X-ray analysis is easier and more accurate using simple well-separated peaks. These aregenerally the lowest order peaks for a given element. K-lines are simpler than L-lines,which are simpler than M-lines. K-lines are also higher energy than L-lines, which are,in turn, higher energy than M-lines. In order to excite characteristic X-rays efficiently,the beam energy must be two to three times the energy of the line of interest. All of thesefactors conspire to make X-ray analysis at higher beam energies very desirable. Lowbeam energies are sometimes used in conventional SEM’s to reduce charging.Unfortunately, X-ray analysis then becomes difficult or impossible. Once again theabsence of charging artifacts in the ESEM frees the analyst to select operatingconditions best suited to the task at hand.

The X-ray signal has intrinsically low resolution and is not suitable for imaging in theconventional sense. In the ESEM, skirt electrons can further degrade X-ray spatialresolution.

When forming a secondary or backscattered electron image, the backgroundcontribution of the skirt electrons is easily discarded while still retaining sufficientsignal to form a high resolution image. This kind of signal processing is a thresholddiscrimination and works well when there is a large difference

Figure 3-12. Gasionization in the

ESEM suppressescharging in insulatingsamples. Left - Silicon

nitride, an insulator,in high vacuum.

Right - The samesample in a 2.8 Torr

water vaporenvironment.

3.3.1 Lack of

Interferences

3.3.2 Sufficient Excitation

Energy

3.3.3 Skirt X-rays

THE ESEM

29

between signal intensity and background intensity. This is not the case for X-rays.The inherently weak X-ray signal is further reduced by the exclusion of all X-rays nothaving the specific energy characteristic of the element of interest. This weak signal issuperimposed on a relatively large background signal (Bremsstrahlung). The poorcounting statistics and low signal to noise ratio make threshold discriminationineffective. Every X-ray counts. Under some conditions, obviously inappropriate for X-ray analysis, skirt electrons generate X-rays at points hundreds of microns from thecenter of the beam. The analyst must always remain aware of the potential for spuriousX-rays generated by skirt electrons.

The skirt is formed by electrons scattered out of the beam by gas molecules. Thedisplacement of a scattered electron from its original destination on the sample surfaceis a function of the scattering angle, and the remaining distance to the sample from thescattering site. Each successive scattering event increases the potential range ofdisplacement. Thus the size of the electron skirt depends on the beam gas path lengthand the sample chamber pressure. Minimizing the path length reduces the likelydisplacement from any one scattering event and reduces the number of times an electronis likely to scatter. Minimizing the pressure also reduces the scattering probability.

In the ESEM, the secondary electron detector is directly above the sample at thebottom of the pole piece. A long working distance version of the ESD lowers the sampleaway from the pole piece while still maintaining a short gas path. In this configuration,the X-ray detector can be positioned close enough to collect X-rays at an efficient thirtydegree take-off angle, while skirt size is kept to a minimum by a gas path length of only2 mm.

There is one other source of X-ray background to be considered. Beam electrons alsoexcite X-rays from the environmental gas. These will appear as a constant low levelsignal characteristic of the gas composition. Again, minimizing pressure and gas pathlength reduces this signal. The gas in the chamber may also be selected to avoid specificinterferences with elements of interest.

X-rays

BSEBSE

SE 15mm

10mm

5mm

20mmBGPL30o

10 Torr-1

Figure 3-13. Aspecially designedESD keeps the gas

path length short whileallowing sufficient

room for a solid statebackscattered electrondetector and an X-raydetector (thirty degreetake-off angle).A short

gas path lengthminimizes X-rays

generated by skirtelectrons.

MinimizingSkirt X-rays

3.3.4 Environmental Gas

X-rays


30

SummaryThere are two key technologies that differentiate the ESEM from all other SEM’s. Thefirst is its multiple aperture, graduated vacuum system. This system maintains a highvacuum in most of the electron column while permitting relatively high pressures in thesample chamber. The gas in the sample chamber does scatter some electrons from thebeam. However, within a scattering regime known as Partial Scattering, correspondingto a certain range of operating conditions (pressure, gas path length, temperature,accelerating voltage, and gas type), beam scattering does not degrade image resolution.

The second key technology is the Environmental or Gaseous Secondary ElectronDetector, using gas ionization to detect and amplify the secondary electron signal. Gasionization also suppresses charging artifacts on insulating samples. The detectors areinsensitive to light and heat.

The ESEM facilitates X-ray analysis by eliminating potential interferences fromcoatings. It also permits the analysis of uncoated insulating samples at higheraccelerating voltages, where X-ray peak structures are less complex. The ESEM doesintroduce additional considerations to X-ray analysis, among them, the influence ofchamber pressure and beam gas path length on X-ray spatial resolution, and thecontribution of X-rays from the environmental gas.

Figure 3-14. Thisseries of micrographs

demonstrates theimaging capability of

the ESEM. The sampleis a zeolite. It is

nonconductive anduncoated. Upper left is

a high resolutionsecondary image taken

at 15 kV in an ESEMwith a field emissiongun at 5 Torr. Upperright is a secondary

image from an ESEMwith a LaB6 electron

gun at 20 kV, 4.9 Torr.The lower left image

was made with a fieldemission gun in high

vacuum using lowaccelerating voltage

(2 kV) to reducecharging. On the

lower right is abackscattered electron

image taken at 20 kVand 1.4 Torr (LV-CSEM conditions)with a LaB6 gun.

31

4 LOW VACUUM - CONVENTIONAL

SEM’S (LV-CSEM’S)

What is an ESEM and what is not? When the ESEM was introduced this was not adifficult distinction to make. It was the only SEM specifically designed with elevatedsample chamber pressure as its primary operating condition. Since the advent of theESEM, several SEM’s have appeared which permit operating pressures intermediatebetween a conventional SEM and an ESEM. Are they ESEM’s or CSEM’s?

The historical context of the ESEM’s development provides a practical definition.The inventors specifically wanted to look at liquid and hydrated samples. This dictatesan operating pressure of at least 4.6 Torr, the minimum vapor pressure required tomaintain liquid water at 0°C. Though somewhat arbitrary, this definition is quite useful,since it derives from one of the most valuable capabilities of the ESEM.

The key enabling technologies of the ESEM are its multiple pressure limitingapertures, and its environmental secondary electron detectors. These technologies areboth protected by patent and available only in the ESEM. They are directly responsiblefor the ESEM’s ability to offer high resolution imaging at pressures above 4.6 Torr and,therefore, may constitute the most specific basis for a definition of the ESEM.

Figure 4-1. The ESEMoperates at pressures

as high as 50 Torr andoffers both SE andBSE imaging. LV-

CSEM’s are limited to2-4 Torr and can offer

only BSE images inlow vacuum mode.

Vacuum in Torr

10 to 10-7 -40.1 1 10 100

4.6 Torr(minimum for liquid water)

500.2 0.5 2 5 20

Secondary and Backscattered Electron Imaging

(1 Torr = 133 Pascal = 1.33 mBar)

Backscattered Imaging Only

ESEM

LV-CSEM

CSEM

SE and BSE

SE and BSE

SE and BSE


32

Other low vacuum SEM’s have no significant technological distinctions fromconventional SEM’s. We will refer to them here as low vacuum conventional SEM’s(LV-CSEM’s) They are readily distinguished from the ESEM, in terms of capability,having, without exception, maximum operating pressures in the 2 to 4 Torr range andno secondary electron imaging capability in low vacuum mode. This chapter looks at thedesign compromises made in LV-CSEM’s, and at their capabilities and limitations.

4.1 VACUUM SYSTEMS

Figure 4-2. An LV-CSEM has only asingle PressureLimiting Aperture(PLA). The size of theaperture determinesthe pressuredifferential that can bemaintained betweenthe column and thesample chamber. Italso limits the currentavailable in theelectron beam

In operation, themechanical pump isisolated from thesample chamber. Thebalance of gas flow infrom the regulatorvalve, with gas flowout through the PLA,sets the pressure in thechamber. Likewise, thebalance of gas flow inthrough the PLA withgas flow out to thepumping system,determines thepressure in thecolumn.

1 Torr

10 Torr-5

PLA

Single

Sample Chamber

GunChamber

High VacuumPump

MechanicalPump

1 Torr

Gas FlowRegulatorValve

LV-CSEM’S

33

The ESEM’s patents restrict LV-CSEM’s to the use of a single pressure limitingaperture. In effect this forces the final aperture to serve a dual function as both apressure limiting aperture and a beam limiting optical aperture. When it is small enoughto sustain a useful pressure difference between the column and the sample chamber, it isalso small enough to limit the current available in the beam. In some designs the finalphysical aperture may directly serve both functions. In other designs, where a projectionaperture higher in the column limits the beam, the final PLA limits the effective size ofthe projection aperture. In either case, the final physical aperture is subject to conflictingoptical and vacuum requirements. These result, ultimately, in performancecompromises.

In an LV-CSEM, a mechanical pump initially evacuates the sample chamber. When thechamber reaches a predetermined pressure, an isolation valve closes between it and themechanical pump. During operation, a diffusion or turbomolecular pump maintainshigh vacuum in the column. Gas flows continuously out of the specimen chamber, intothe column, through the PLA. A regulator valve meters gas into the sample chamber at arate controlled by the operator. The chamber and column settle to equilibrium pressures,determined by the various gas flows, and manipulated by the regulator valve.

In the column, the vacuum level is determined by the balance between gas outflow,to the high vacuum pumping system, and gas inflow, through the PLA. Since thevacuum level required in the column and the high vacuum pumping capacity are bothfixed for any system, they also fix the maximum inflow permitted through the PLA. Gasflow through an aperture is proportional to the pressure difference and the area of theopening, for a given gas, temperature, and type of flow. At the maximum permitted PLAflow rate, the size of the aperture therefore determines the pressure differential betweenthe chamber and the column and, consequently, the maximum permitted pressure in thechamber. Smaller apertures permit higher pressures but reduce beam current. Largerapertures permit higher beam current but reduce chamber pressure.

Increasing the performance of the vacuum system is not as simple as increasing thesize and speed of the pumps. Since the mechanical pump is isolated after initial

4.1.1 Single Pressure

Limiting Aperture

Aperture Size

Beam GasPath Length

2 mm

15-20 mm

ESEM LV-CSEM

BSED

Figure 4-3. The LV-CSEM must combine

both optical andvacuum functions in a

single aperture. Thecompromise requires a

smaller aperture andlonger beam gas path

length than the ESEM.


34

evacuation, a faster pump may improve pump down time, but does not affect themaximum operating pressure in the sample chamber. In the high vacuum system of thecolumn, performance is determined by the combination of the pump capacity, and thepipe conductance between the pump and the column. In practice, pipe conductance isthe more difficult to improve. Most systems, particularly adaptations of conventionaldesigns, are pipe limited.

In an ESEM, the use of multiple apertures permits smaller pressure differences, andtherefore larger diameters, at each aperture, while still maintaining a greater totalpressure difference between the column and the sample chamber. These larger aperturesdo not impose a practical limit on beam current. Moreover, the entire vacuum system ofthe ESEM is designed for optimal performance in the environmental pressure range.

The same principles that govern electron scattering in the ESEM, also apply in the LV-CSEM. In order to maintain their imaging capability, they too must operate in thepartial scattering regime. In the equations for electron scattering, pressure and beam gaspath length are equivalent. That is, an increase in path length has exactly the sameeffect as an increase in pressure. For a given degree of scattering, shorter path lengthspermit higher pressures.

Ideally, then, the final PLA, should be as close as possible to the sample surface.However, an optical aperture in this position (close to the focal plane of the lens), limitsthe field of view. For the large apertures used in an ESEM (500 to 1000 micrometers),this limit is not overly restrictive. The small PLA’s (typically 75 to 200 micrometers),required to attain useful chamber pressures in an LV-CSEM, make this positionimpractical.

SEM’s use scan coils located above the final lens plane to move the beam throughthe scanning pattern. Most use a technique called double deflection, in which the beamis first diverted to one side, and then back again the opposite direction, to pass throughthe principal plane of the lens at the optical axis. This point, about which the beampivots as it scans, is sometimes called the rocking point. An aperture at this point limitsbeam current equally for all points in the image plane, and can be a minimum sizewithout limiting the field of view. In an LV-CSEM, the need to pass a maximum currentthrough a minimum aperture dictates that the aperture be located here. Unfortunately,this point is typically 5-10 mm above the bottom of the pole piece. Since most LV-CSEM’s require an additional 5-10 mm of working distance below the pole piece, thebeam gas path length is 10 to 20 mm, an order of magnitude greater than in the ESEM.The result is a fundamental limitation — to remain in the partial scattering regime, LV-CSEM’s must operate at pressures an order of magnitude less than an ESEM.

The design of an LV-CSEM vacuum system, with a single PLA, requires a variety ofcompromises between optical and vacuum considerations. How do these technicalcompromises translate into practical limitations?

LV-CSEM’s have maximum chamber pressures in the range of 2 to 4 Torr. Probably themost significant sacrifice to lower sample chamber pressure is the loss of the capabilityto keep wet samples wet. The minimum pressure needed to sustain liquid water is about4.6 Torr. At lower pressures wet samples desiccate quickly and unavoidably. Lowchamber pressures also preclude sample wetting and relative humidity experiments.

Aperture Position

4.1.2 Performance

Limitations

Upper Pressure Limit

LV-CSEM’S

35

Figure 4-4. This set ofmicrographs

demonstrates theimportance of adequate

pressure capability inmaintaining hydrated

samples. The sample isan orchid petal. The

upper pair were takenbefore and after a two

minute exposure to a 1.4Torr water vapor

environment at 6 degreesC. Dehydration is

obvious. The lower pairis the same sample

before and after a thirtyminute exposure to a 7.0

Torr water vaporenvironment at 6 degrees

C. At this temperatureand pressure, the water

vapor environmentbecomes saturated and

dehydration does notoccur.

Figure 4-5. Theminimum pressure that

can sustain water inthe liquid phase is

about 4.6 Torr at 0degrees C. Higher

temperatures requirehigher pressures.

Relative Humidity Isobars

0

5

10

15

20

25

0 5 10 15 20 25

Temperature (°C)

Pre

ssu

re (

To

rr)

Liquid Phase

Gas Phase

100%

60%

80%

40%

20% LV-C

SE

M

ES

EM


36

Imaging current is the unscattered electron current, remaining in the spot on the samplesurface, from which high resolution images are formed. The LV-CSEM pays a doublepenalty in imaging current. Vacuum requirements prevent the use of larger apertures toincrease overall beam current. Long beam gas path lengths multiply losses due toscattering. The table below compares scattering losses in the ESEM with those in anLV-CSEM.

Imaging Current - Room Temperature, Water Vapor, 20 kVPressure % of Primary Beam Current

Torr Pascals ESEM LV-CSEMBGPL = 2 mm BGPL = 20 mm

40 5320 5%20 2660 23%10 1330 48% 0.1%7 931 60% 0.6%5 665 69% 2.5%2 266 86% 23%1 133 93% 48%

0.5 66.5 96% 69%

In the LV-CSEM, any gas or contamination that passes the single PLA has direct accessto the gun chamber. This leads to concerns about the types of gas permitted. Most LV-CSEM’s permit only air or dry nitrogen. Every ESEM includes an auxiliary gasmanifold and permits the use of practically any gas.

Contamination of the beam limiting aperture distorts the shape of the beam, causingastigmatism in the image. In systems using the same aperture to limit both current andpressure, the aperture is directly exposed to contamination from the sampleenvironment. In the ESEM two PLA’s protect the projection aperture fromcontamination.

Contamination of the chamber does not usually interfere with imaging in lowvacuum mode. However the same levels of cleanliness that cause no problems in lowvacuum mode can lengthen pump down times or completely prevent operation in highvacuum mode. Because of their limitations in low vacuum mode, LV-CSEM’s aretypically used as conventional high vacuum SEM’s most of the time, reserving lowvacuum operation for occasional use in special applications. If their high vacuumperformance is to be maintained, they must either avoid contaminating samples or beshut down for cleaning after each low vacuum use. Unfortunately, this often leads to areluctance to use of the low vacuum capabilities at all. In the ESEM there is noperformance penalty in low vacuum mode. Most ESEM’s, though perfectly capable ofhigh vacuum operation, are used almost exclusively in environmental mode.

Because of its location in the lens plane, the PLA in an LV-CSEM does not limit thefield of view. Although the PLA does limit the field of view in the ESEM, the use ofrelatively large apertures provides sufficient field for most applications. When optimizedfor large field imaging, the ESEM offers full field magnifications of less than 50X,corresponding to field sizes greater than 2 mm. It is worth noting that the ESEM canoperate in high vacuum mode as well, with no PLA and an unrestricted field of view.

Imaging Current

Environmental Gases

Contamination

Field of View

LV-CSEM’S

37

4.2 SIGNAL DETECTION — BSE ONLY

One of the most important differences between the ESEM and LV-CSEM’s lies in theirsignal detection systems. The ESEM uses a proprietary Environmental SecondaryDetector to detect secondary electrons in the gaseous environment. Because conventionalsecondary electron detectors cannot function in a low vacuum environment, LV-CSEM’scan provide only backscattered electron images in low vacuum mode.

The micrographs in Figure 4-6 compare secondary and backscattered images fordifferent samples. Note that the resolution loss is strongly dependent on the sample type.Among manufacturers and users of SEM’s, gold on carbon has become a de factostandard for demonstrating image resolution, and with good reason. Gold’s high atomicnumber limits resolution loss due to beam penetration and its complex topography offersplenty of secondary electron contrast. This sample also offers tremendous atomicnumber contrast between gold and carbon. It is perhaps the best possible sample tominimize resolution loss in a comparison of secondary and backscattered electronimages. The toner particle micrographs, a low atomic number sample, show muchgreater resolution difference.

Figure 4-6. Themicrographs on the

left are secondaryelectron images taken

in the ESEM atpressures of 7.6 and

5.4 Torr. On the rightare backscattered

electron images of thesame samples at 1.0

and 0.7 Torr. Theydemonstrate the

resolution capabilitiesof the ESEM and LV-

CSEM’s under typicaloperating conditions.

Note the strongdependency in the

BSE images on sampletype. The low atomic

number tonerparticles (30,000 X)

have noticeablypoorer resolution thanthe high contrast, high

atomic number goldon carbon (50,000X).

4.2.1 Resolution


38

Although charging has less effect on higher energy backscattered electrons, gasionization in the LV-CSEM may still be insufficient to eliminate charging artifacts onsome samples. Lacking the ions created by the ESD’s gas amplification, the LV-CSEMmust rely solely on ions created by the beam. Unfortunately, every ionization caused by abeam electron removes that electron from the imaging current. The result is a directtrade of imaging current for charge suppression. In situations where low chamberpressure is required, as during X-ray analysis, it may be impossible to maintainsufficient current for imaging and sufficient ionization for charge suppression.Operationally, charge suppression in the LV-CSEM may be controlled only by adjustingaccelerating voltage or chamber pressure, neither of which is very convenient. In theESEM, positive ions are created both by beam electrons and by accelerated secondaryelectrons as part of the cascade amplification of the ESD. Varying the ESD fieldstrength provides convenient control of charge suppression.

Conventional secondary and backscattered electron detectors use light sensitivecomponents as part of the detection chain. They also include materials that do nottolerate high temperatures. As a result, they are not suitable for a wide range ofapplications. They cannot be used to observe fluorescent, cathodoluminescent, orincandescent samples. They are limited, either directly, by transferred heat or, indirectly,by sample incandescence, in their ability to observe hot samples. They preclude the useof light microscopy for collateral observations. Finally, they prevent the use of a sampleviewport and chamber illuminator during electron image acquisition.

4.3 X-RAY ANALYSIS

X-ray analysis in a gaseous environment requires additional considerations. Principalamong them is minimizing skirt size by using a short beam gas path length and lowpressure. In the calculation of beam current loss for the partial scattering regime,pressure and path length are equivalent. They can be freely traded, one for the other,without increasing scattering losses. The same is not true with respect to skirt size. Skirtsize is a function of the average scattering angle and the path length. Think of the skirtsize as the base of a cone with its apex at the PLA. For a given average scattering angle,fixed by the type of gas and accelerating voltage, the diameter of the base is proportionalto the height of the cone.

4.2.2 Charge Suppression

Figure 4-7. ThoughBSE’s are less

sensitive to chargingthan SE’s, interference

can still occur. Theimage on the left wastaken at 0.2 Torr, 20mm gas path, on theright at 0.9 Torr, 20

mm gas path. Imagingmay be difficult when

low pressure isrequired, e.g. during

X-ray analysis.

4.2.3 Sensitivity to Light

and Heat

LV-CSEM’S

39

A path ten times longer yields a skirt ten times broader. The long gas path lengthsrequired in the LV-CSEM multiply the difficulties caused by skirt generated X-rays.

4.4 SUMMARY

Because LV-CSEM’s are unable to offer the key technologies of the ESEM — themultiple aperture, graduated vacuum system and the Environmental or GaseousSecondary Electron Detector — they incorporate a series of compromises. Theiroperating pressures are limited by conflicting optical and vacuum demands placed onthe single pressure limiting aperture. They cannot maintain liquid water in the chambernor keep a hydrated sample from drying. Their small apertures limit total beam current.The multiplied effects of scattering over an increased gas path length further limit theirimaging current. They lack any secondary electron imaging capability in low vacuummode. They have insufficient gas ionization to suppress charge on some samples. Theyare sensitive to light and heat. Their broad electron skirts complicate X-ray analysis.

LV-CSEM’s perform best as conventional high vacuum SEM’s with occasional usein low vacuum mode. In some cases, charge suppression for instance, their distinctionfrom the ESEM is a question of degree. However, in most cases — secondary electronimaging, hydrated samples, environmental gas selection, X-ray analysis, and more —they do not offer equivalent capability in any degree.

2 mm

ESEM

θ

LV-CSEM

BSED θ

r

15-20 mm

r

Skirt Radius and Beam Gas Path Length

Figure 4-8. Skirt sizeis a function of beam

gas path length andaverage scattering

angle. The long BGPLrequired in an LV-

CSEM results in skirtsizes many timesgreater than the

ESEM. Large skirtsgenerate X-rays farfrom the analytical

target.The X-rayspectra shown herewere acquired fromthe same sample, a

crystal of Epsom saltnearly 900 microns in

size. Even on thislarge sample the LV-

CSEM spectrum showspeaks generated by

skirt electrons fallingon the aluminum stub

and carbon paintholding the sample. Al

and C peaks areabsent in the ESEM

spectrum.

40

5 APPLICATIONS

This chapter contains a selection of images chosen, each, to represent a class of similarapplications, and as a collection, to demonstrate the tremendous range of ESEMapplications. This is by no means an exhaustive survey. For additional examples pleasesee the ESEM Image Library and the ESEM Bibliography.

5.1 NONCONDUCTIVE SAMPLES - UNCOATED

Figure 5-1, Left -Silicon nitride

Right - Ceramic

Figure 5-2, Left -Partially fossilized

dinosaur boneRight - Aquatic fern

megaspore (135million year old fossil)

APPLICATIONS

41

NONCONDUCTIVE SAMPLES - UNCOATED (CONTINUED)

Figure 5-3, Left -Fern spore (140

million year old fossil)Right - Foraminifer

Figure 5-4, Left -Hole in photoresist

during integratedcircuit fabrication

processRight -

Pharmaceuticalinhaler crystals

Figure 5-5, Left -Artificial sweetener

crystalsRight - Rouge on

nylon from a forensicinvestigation


42

5.2 HYDRATED SAMPLES

Figure 5-6, Left -Orchid petal after

thirty minute exposureto saturated water

vapor environmentRight - Poinsettia leaf,

fully hydrated

Figure 5-7, Left -Poinsettia pollen

Right - PassionFlower pollen

Figure 5-8, Left -Stomata on an Aloe

Vera leafRight - Root hairs of a

beet seedling

APPLICATIONS

43

HYDRATED SAMPLES (CONTINUED)

Figure 5-9, Left - Rattooth at 80X

Right - Living aphid

Figure 5-10, Left -Sweat pore, porcine

abdominal skinRight - Skin of a

human finger tip,forensic sample

Figure 5-11, Left -Human hair with

water dropletsRight - Wet paper


44

HYDRATED SAMPLES (CONTINUED)

5.3 CONTAMINATING SAMPLES

Figure 5-12, Left -Bacteria and red

blood cells on toothroot tissue

Right - Water film ona copper grid

Figure 5-13, Left -Crystallized structure

discovered in oilsaturated sandstone

Right - Droplets of oiland water on a

geological sample

Figure 5-14, Left -Crystal fibers in water

saturated sand stoneRight - Metal particles

in uncured resin

APPLICATIONS

45

CONTAMINATING SAMPLES (CONTINUED)

5.4 DELICATE SAMPLES

Figure 5-15, Left -Outgassing antacid

particles dissolving inwater

Right - Bacon bit

Figure 5-16, Left -Fungus on a pine

needleRight - Fungal hyphae

with calcium oxalatecrystals

Figure 5-17, Left -Bread mold

Right - Moth wingscales


46

5.5 COATING INTERFERENCE

5.6 PHASE TRANSITIONS

Figure 5-18Left - Styrofoam at

9.1 kVRight - The same

sample at 24 kV. Thedifference in the two

micrographs is due tothe greater

penetration of thehigher energy beam. If

the sample had beencoated with gold for

conductivity, theinternal structurewould have been

masked.

Figure 5-19, Left -Lung tissue labeledwith 20 nanometer

gold particles. A goldcoating would have

obscured the labelingparticles

Figure 5-20, Left -Surface of pure silicon

melted andresolidified in the

ESEM.Right - Solder on

copper melted in theESEM. With a high

temperature hot stage,the ESEM can provide

electron images ofsamples at

temperatures as highas 1500°C.

APPLICATIONS

47

PHASE TRANSITIONS (CONTINUED)

5.7 HYDRATION PROCESSES

Figure 5-21, Left -Potassium chloride

crystals grown fromvapor in the ESEM at

about 600°C.Right - Camphor

sublimating to vapor

Figure 5-22, Left - Icecrystallized from

vapor in the ESEMRight - Crystal of

hydrochloric acid iceformed over a layer of

water ice on Pyrex.

Figure 5-23, Left -Crystals of table salt

begin to dissolve inwater condensed from

the chamberatmosphere

Right - Portlandcement wetted by

water condensed fromthe ESEM atmosphere


48

5.8 OXIDATION/CORROSION

5.9 THERMAL/MECHANICAL/CHEMICAL STRESS

Figure 5-24, Left -Oxide grows around asmall sulfur inclusion

in a piece of iron at860°C in a pure

oxygen atmosphereRight - Iron sulfide

crystals grown onstainless steel

Figure 5-25, Left - Adroplet of liquid

toluene has etchedaway the matrix of a

plastic compositeRight - In a high

temperature oxidizingenvironment, cracks

develop at thefiber/matrix interface

of a silicon carbidereinforced composite.

Figure 5-26, Left -Separation occurs at

the fiber/matrixinterface during

tensile failure of apolypropylene

reinforced cementRight - Cracks

develop at hightemperature in a

carbon-carboncomposite

INDEX

49

Further Reading

G. D. Danilatos, “Foundations ofEnvironmental Scanning ElectronMicroscopy,” in Advances inElectronics and Electron Physics71, 109–250, 1988

J. I. Goldstein, D. E. Newbury, P.Echlin, D. C. Joy, A. D. Romig, C.E. Lyman, C. Fiori, E. Lifshin,Scanning Electron Microscopy andX-ray Microanalysis, 2nd Edition(Plenum Press, New York, 1992)

K. F. J. Heinrich, Electron Beam X-rayMicroanalysis (Van NostrandReinhold, New York, 1981)

J. E. Johnson, E. M. Griffith, G. D.Danilatos, eds. MicroscopyResearch and Technique 25(5&6),August 1993

ElectroScan Corporation Bibliography

ElectroScan CorporationESEM BIBLIOGRAPHY 1 Wednesday, May 13, 1998

rev. 8

ElectroScan Corporation

ESEM BibliographySeptember 1997

Issue 11

THE ©1995-1998 FEI Company ESEM BIBLIOGRAPHY CONTAINS LISTINGS ON PAPERS PUBLISHED.

*Information in this Directory is subject to change without notice.

TO ADD INFORMATION TO THIS DIRECTORYPLEASE FILL OUT THE FORM IN THE BACK OF THIS DIRECTORY , AND SEND TO:

ESEM BIBLIOGRAPHY UPDATEFEI Company

66A CONCORD STREETWILMINGTON, MA 01887.

TABLE OF CONTENTSINDEX BY KEY WORDS

SHORT FORM LIST OF PAPERS

Update History:

August 1994 ...................................Release.October 1994 .................................Alfred Pick Updates added. Lit. 277 - 289April 1995 .......................................Lit 290 added per E-Mail (Mike Ellis found on Internet).January, 1995.................................added MRT Bibliography pages Lit. 291.April 1995 .......................................added Lit 292-294 per Ralph KnowlesMay 1995........................................added Lit 151 191, from stockroom inventory w/ T. RiceMay 1995........................................added/changed/deleted duplicates Lit 294-316 w/ T. RiceJune 1995.......................................added papers from Internet and Danilatos bibliographyOctober 1995 .................................added pages from WWW, and InstrumatMarch 1996 ....................................added Lit. 325-350, per E. Doehne, Getty Conservation Inst.November 1996......................dded Lit. 351- 368, per Ralph KnowlesAugust 1997 ..................................Major update by Helen Knowles



rev. 8

Contents

151 Neil Baumgarten, SEM for imaging specimens in their natural state, American Laboratory June 1990 ....... 1

152 K. Sujata, Hamlin M. Jennings, Advances in Scanning Electron Microscopy, MRS Bulletin, March 1991 ... 1

153 Roger Bolon, C.D. Robertson, Eric Lifshin, The Environmental SEM: A New Way To Look At Insulators,P.E. Russell, Ed., Microbeam Analysis, 1989 © 1989 San Francisco Press, Inc., USA ................................... 1

157 G.D. Danilatos, Journal of Microscopy Review, Vol. 162, Pt.3, June 1991 Received 30 April 1990; revisedand accepted 11 July 1990. ............................................................................................................................ 1

158 Faith Taylor, Thomas A. Hardt, New Approaches to Ceramic Research Using the Environmental ScanningElectron Microscope., ElectroScan Corporation, Wilmington, MA 01887.................................................... 2

159 Klaus-Ruediger Peters, Environmental Cryo-Scanning Electron Microscopy, Proceedings of Scanning, ‘91.2

160 C.D. Robertson, J. Stein, M.L. Porta, R.B. Bolon, M.E. Grenoble A Study of Silicon Release Coatings,Proceedings of Scanning ‘91.......................................................................................................................... 2

161 Roger B. Bolon, ESEM, the Technique and Application to Materials Characterization, Scanning Vol. 13,Supplement I, 1991........................................................................................................................................ 2

162 Robert K. Pope and Raymond Scheetz, Colonization Of Copper Surfaces By Sulfate-Reducing BrendaLittle, Patricia Wagner, and Richard Ray, Naval Oceanographic and Atmospheric Research Laboratory,Proceedings of SCANNING 91, 1-93. ............................................................................................................ 2

163 Klaus-Reudiger Peters, David G. Rhodes, Roderike Pohl, Chemical Cryo-stabilization of Lipid Monolayersand Bilayers, Scanning Vol. 13, Supplement I, 1991. ................................................................................... 3

165 S. Mehta, ARCO Oil & Gas Co., SPE Member, Imaging of Wet Specimens in Their Natural State UsingEnvironmental Scanning Electron Microscope (ESEM): Some Examples of Importance to PetroleumTechnology, SPE 22864, Copyright 1991. Society of Petroleum Engineers Inc.............................................. 3

167 B. Little, P. Wagner, J. F. Mansfield, Microbiologically influenced corrosion of metals and alloys, © 1991The Institute of Metals and ASM International. International Materials Review, 1991 Vol. 36 No. 6, pp. 253-272. ............................................................................................................................................................... 3

171 K.-R. Peters, L.A. Firstein, A. Noz, Environmental SEM and Conventional SEM Imaging of Electron-Sensitive Resist: Contrast Quality and Metrological Applications, Microelectronic Engineering 17 (1992),pp. 455-458, Elsevier. .................................................................................................................................... 3

172 K.-R. Peters, Principles of Low Vacuum Scanning Electron Microscopy, Molecular Imaging Laboratory,Biomolecular Structure Analysis Center, University of Connecticut, Farmington, CT 06030-2017................ 4

173 Anthony D’Emanuele,, Ph.D., ESEM - A New Research Tool In Pharmaceutical Science. ......................... 4

174 Anthony D’Emanuele, Joseph Kost, Jennifer Hill, Robert Langer, An Investigation of the Effects ofUltrasound on Degradable Polyhydride Matrices., © 1992 by the American Chemical Society andReprinted by permission from Macromolecules, 1992, 25. ............................................................................. 4

175 Patricia A. Wagner, Brenda J. Little, Richard I. Ray, Naval Oceanographic and Atmospheric ResearchLaboratory, Joanne Jones-Meehan, Naval Surface Warfare Center, Investigations of MicrobiologicallyInfluenced Corrosion Using Environmental Scanning Electron Microscopy., Corrosion ‘92 The NACEAnnual Conference and Corrosion Show, Paper #185. ................................................................................... 4

176 Patricia A. Wagner, Brenda J. Little, Richard I. Ray, Raymond Scheetz, Robert Pope, Biofilms: an ESEMevaluation of artifacts introduced during SEM preparation., Journal of Industrial Microbiology, 8, 1991,pp. 213-222, Elsevier ..................................................................................................................................... 4



rev. 8

177 Sudhir Mehta, Environmental Scanning Electron Microscope (ESEM): A New Imaging and AnalysisTechnique of Reservoir Rocks, ARCO, SPE22864, © 1991 SPE Annual Technical Conference in Dallas. .. 5

178 Howard S. Kaufman*, Keith D. Lillemoe*, John T. Mastovich**, and Henry A. Pitt* *Department of Surgery,The Johns Hopkins Medical Institutions, Baltimore, Maryland and **Fisons Instruments, Danvers,Massachusetts, Environmental Scanning Electron Microscopy Of Fresh Human Gallstones Reveals NewMorphologies Of Precipitated Calcium Salts, G.W. Bailey. J. Bentley, and J. A. Small. Editors, Proc. 50thAnnual Meeting of the Electron Microscopy Society of America. Held jointly with the 27th Annual Meetingof the Microbeam Analysis Society and the 19th Annual Meeting of the Microscopical Society ofCanada/Société de Microscopic du Canada Copyright © 1992 by EMSA. Published by San Francisco Press.Inc.- Box 426800. San Francisco, CA 94142-6800, USA .............................................................................. 5

179 Robert J. Koestler, Norman Indictor, and Richard Harneman, Ancient Near Eastern Ivories Imaged andAnalyzed with Environmental Scanning Electron Microscopy and Conventional Scanning ElectronMicroscopy., The Metropolitan Museum of Art, New York, NY and Brooklyn College, CUNY, Brooklyn,NY ................................................................................................................................................................ 5

180 Hemant S. Betrabet, J.K. McKinlay, S.B. McGee, Dynamic Observations of Sn-Pb Solder Reflow in aHotstage Environmental Scanning Electron Microscope. .......................................................................... 5

181 E.R. Prack, C.J. Raleigh, Environmental SEM in the Characterization of Electronics Industry Process.,Corporate Mfg. Research Center, Motorola Inc., Schaumberburg, Ill 60196................................................... 6

183 J.C. Baker, P.J.R. Uwins, I.D.R. Mackinnon, ESEM Study of Authigenic Chlorite Acid Sensitivity inSandstone Reservoirs, Journal of Petroleum Science and Engineering, March 1992. .................................... 6

184 J.C. Baker, P.J.R. Uwins, I.D.R. Mackinnon, ESEM Study of Illite-smectite freshwater sensitivity insandstone reservoirs, Journal of Petroleum Science and Engineering, June 1992.......................................... 6

185 H. M. Wallace, P.J.R. Uwins and C. A. McConchiel, Investigation of pollen-stigma interactions inMacadamia and Grevillea using ESEM, Department of Entomology, University of Queensland, St. ........... 6

Lucia, Qld 4072, Australia, Electron Microscope Centre, University of Queensland, St. Lucia, Qld 4072, Australia,CSIRO Division of Horticulture, 306 Carmody Rd, St. Lucia, Qld 4067, Australia......................................... 7

186 O'Brien, G.P, Webb, R.I. Uwins P.J.R., Desmarchelier P.M,. Imrie B.C., Suitability Of The EnvironmentalScanning Electron Microscope For Studies Of Bacteria On Mungbean Seeds, Department ofMicrobiology, University of Queensland, QLD 4072., Tropical Health Program, University of Queensland.Centre for Microscopy and Microanalysis, University of Queensland, CSIRO Division of Tropical Crops andPastures, Cunningham Laboratory, Qld 4067. ................................................................................................ 7

187 M.J. Klose, R.I. Webb, D.S. Teakle, Studies on the Association of Tobacco Steak Virus and Pollen Usingan Environmental Scanning Electron Microscope (ESEM) and Molecular Distillation Technique.,Department of Microbiology and Centre for Microscopy and Microanalysis, University of Queensland, QLD4072. ............................................................................................................................................................. 7

200 Danilatos, G.D. , and Robinson, V.N.E. (1979) Principles of scanning electron microscopy at highpressures. Scanning 2:72-82. ....................................................................................................................... 7

201 Danilatos, G.D. (1980a) An atmospheric scanning electron microscope (ASEM). Scanning 3:215-217. .... 8

202 Danilatos, G.D. (1980b) An atmospheric scanning electron microscope (ASEM). Sixth AustralianConference on Electron Microscopy and Cell Biology, Melbourne (18-22 February, 1980), Proc. in Micron11:335-336. ................................................................................................................................................... 8

203 Danilatos, G.D., Robinson, V.N.E., and Postale, R. (1980) An environmental scanning electron microscopefor studies of wet wool fibers. Proc. Sixth Quinquennial Wool Textile Research Conference (26 Aug.-3Sept., 1980), Pretoria, II:463-471................................................................................................................... 8



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204 Danilatos, G.D. (1981a) The examination of fresh or living plant material in an environmental scanningelectron microscope. J. Microsc. 121:235-238. ............................................................................................ 8

205 Danilatos, G.D. (1981b) Design and construction of an atmospheric or environmental SEM (part 1).Scanning 4:9-20. ........................................................................................................................................... 8

206 Danilatos, G.D., Loo, S.K., Yeo, B.C. and McDonald, A. (1981) Environmental and atmospheric scanningelectron microscopy of biological tissues. 19th Annual Conference of Anatomical Society of Australia andNew Zealand, Hobart, J. Anatomy 133:465. ................................................................................................... 9

207 Danilatos, G.D., and Postale, R. (1982a) Advances in environmental and atmospheric scanning electronmicroscopy. Proc. Seventh Australian Conf. El. Microsc. and Cell Biology, Micron 13:253-254. ................. 9

208 Danilatos, G.D., and Postale, R. (1982b) The environmental scanning electron microscope and itsapplications. Scanning Electron Microscopy 1982:1-16. .............................................................................. 9

209 Danilatos, G.D., and Postale, R. (1982c) The examination of wet and living specimens in a scanningelectron microscope. Proc. Xth Int. Congr. El. Microsc., Hamburg, 2:561-562............................................. 9

210 Danilatos, G.D. (1983a) Gaseous detector device for an environmental electron probe microanalyzer.Research Disclosure No. 23311:284. .............................................................................................................. 9

211 Danilatos. G.D. (1983b) A gaseous detector device for an environmental SEM. Micron and MicroscopicaActa 14:307-319. ......................................................................................................................................... 10

212 Danilatos, G.D., and Postale, R. (1983) Design and construction of an atmospheric or environmental SEM-2. Micron 14:41-52. .................................................................................................................................... 10

213 Danilatos, G.D. (1984) The gas as a detection medium in the environmental SEM. Eighth AustralianConference on Electron Microscopy, Brisbane, Australian Academy of Science, Abstracts:9........................ 10

214 Danilatos, G.D., and Brancik, J.V. (1984) A microinjector system in the environmental SEM. EighthAustralian Conference on Electron Microscopy, Brisbane, Australian Academy of Science, Abstracts:34..... 10

215 Danilatos, G.D., Denby, E.F., and Algie, J.E. (1984) The effect of relative humidity on the shape of Bacillusapiarius spores. Current Microbiology 10:313-316. .................................................................................... 11

216 Danilatos, G.D. (1985) Design and construction of an atmospheric or environmental SEM (part 3).Scanning 7:26-42......................................................................................................................................... 11

217 Danilatos, G.D., and Brooks, J.B. (1985) Environmental SEM in wool research present state of the art.Proc. 7th Int. Wool Textile Research Conference, Tokyo, I:263-272. ........................................................... 11

218 Danilatos, G.D. (1986a) Environmental and atmospheric SEM - an update. Ninth Australian Conferenceon Electron Microscopy, Australian Academy of Science, Sydney, Abstracts:25........................................... 11

219 Danilatos, G.D. (1986b) Color micrographs for backscattered electron signals in the SEM. Scanning 8:9-18. ............................................................................................................................................................... 11

221 Danilatos, G.D. (1986d) Improvements an the gaseous detector device. Proc. 44 Annual MeetingEMSA:630-631............................................................................................................................................ 12

222 Danilatos, G.D. (1986e) ESEM - A multipurpose surface electron microscope. Proc. 44th Annual MeetingEMSA:632-633............................................................................................................................................ 12

223 Danilatos, G.D. (1986f) Beam-radiation effects on wool in the ESEM. Proc. 44th Annual MeetingEMSA:674-675............................................................................................................................................ 12

224 Danilatos, G.D. (1986g) Specifications of a prototype environmental SEM. Proc. XIth Congress onElectron Microscopy, Kyoto, I:377-378........................................................................................................ 12



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225 Danilatos, G.D. (1986h) Cathodoluminescence and gaseous scintillation in the environmental SEM.Scanning 8:279-284..................................................................................................................................... 12

226 Danilatos, G.D., and Brancik, J.V. (1986) Observation of Liquid transport in the ESEM. Proc. 44thAnnual Meeting EMSA:678-679. ................................................................................................................ 13

227 Danilatos, G.D. (1988a) Foundations of Environmental Scanning Electron Microscopy. Advances inElectronics and Electron Physics, Academic Press, Vol. 71:109-250. ........................................................... 13

228 Danilatos, G.D. (1988b) Electron beam profile in the ESEM. Proc. 46th Annual Meeting EMSA:192-193.14

229 Danilatos, G.D. (1988c) Contrast and resolution in the ESEM. Proc. 46th Annual Meeting EMSA:222-223.14

230 Danilatos, G.D. (1989a) Surface chemistry in the ESEM. Pittsburgh Conference and Exposition (Atlanta)1989, Abstracts, paper No. 360. ................................................................................................................... 14

231 Danilatos, G.D. (1989b) Environmental SEM: a new instrument, a new dimension. Proc. EMAG-MICRO89, Inst. Phys. Conf. Ser. No 98, Vol. 1:455-458. (also Abstract in: Proc. Roy. Microsc. Soc. Vol. 24, Part 4,p. S93)......................................................................................................................................................... 14

232 Richard Harneman ESEM Uses Vacuum Gradients to Examine Wet and Uncoated NonconductiveSamples, Research & Development September 1988 © 1988 Cahners Publishing Company ........................ 14

233 Danilatos, G.D. (1990a) Design and construction of an environmental SEM (part 4). Scanning 12:23-27.(originally submitted , Nov. 1987) ............................................................................................................... 14

234 Danilatos, G.D. (1990b) Fundamentals of environmental SEM. Eleventh Australian Conf. El. Microsc.,University of Melbourne, Abstracts. ............................................................................................................. 14

235 Danilatos, G.D. (1990c) Theory of the Gaseous Detector Device in the ESEM. Advances in Electronicsand Electron Physics, Academic Press, Vol. 78:1-102. ................................................................................. 15

236 Klaus-Ruediger Peters, Surface Imaging of the Natural Air Interface of Hydrated Lung Tissue, MolecularImaging Laboratory, Dept. of Radiology Biomolecular Structure Analysis Center, University of ConnecticutHealth Center, Farmington, CT ................................................................................................................... 15

237 Klaus-Ruediger Peters, Introduction to the Technique of Environmental Scanning Electron Microscopy,Molecular Imaging Laboratory, Dept. of Radiology Biomolecular Structure Analysis Center, University ofConnecticut Health Center, Farmington, CT ................................................................................................ 15

238 Danilatos, G.D. (1990f) Detection by induction in the environmental SEM. Electron Microscopy 1990,Proc. XIIth Int. Confer. El. Microsc. (Ed. Peachey and Williams), San Francisco Press, Vol. 1:372-373. ..... 15

239 Danilatos, G.D. (1991a) Review and outline of environmental SEM at present. J. Microsc. 162:391-402. 16

240 Danilatos, G.D. (1991b) Gas flow properties in the environmental SEM. Microbeam Analysis-1991 (Ed. DG Howitt), San Francisco Press, San Francisco:201-203. ............................................................................. 16

241 Danilatos, G.D. (1992b) Gas flow in the ESEM Proc. ACEM-12 & ANZSCB-11 Univ. of Western Australia,Perth:57. ...................................................................................................................................................... 16

242 Danilatos, G.D. (1992b) Gas flow in the environmental SEM. Proc. 50th Annual Meeting EMSA (Ed G.W.Bailey, J Bentley and JA Small), San Francisco Press, San Francisco:1298-1299. ........................................ 16

243 Danilatos, G.D. (1992c) Secondary-electron imaging by scintillating gaseous detection device. Proc. 50thAnnual Meeting EMSA (Ed G.W. Bailey, J Bentley and JA Small), San Francisco Press, San Francisco:1302-1303. ........................................................................................................................................................... 16

244 Danilatos, G.D. (1993a) Environmental scanning electron microscope-some critical issues. .................... 16



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245 Danilatos, G.D. (1993b) Environmental scanning electron microscopy and microanalysis. MikrochimiaActa, submitted............................................................................................................................................ 17

246 Danilatos, G.D. (1993c) Environmental scanning electron microscope: A new tool for inspection andtesting. Jap. J. Appl. Phys. (submitted). ...................................................................................................... 17

247 Danilatos, G.D. (1993d) Universal ESEM. Proc. 51st Annual Meeting EMSA, submitted........................... 18

248 Danilatos, G.D. (1993e) An introduction to ESEM instrument. Microsc. Res. Technique, in press............. 18

249 Danilatos, G.D. (1993f) Biography of environmental scanning electron microscopy. Microsc. Res. andTechnique, in press...................................................................................................................................... 18

250 C.E. Jordan and A.R Marder, A Model For Galvanneal Morphology Development The Physical Metallurgyof Zinc Coated Steel..................................................................................................................................... 18

251 Weiying Tao and Billie J. Collier. The Environmental Scanning Electron Microscope: A new Tool forTextile Studies............................................................................................................................................ 19

252 Y.Xi, T.B. Bergstrom and H.M. Jennings, Image intensity Matching Technique: Application to theEnvironmental Scanning Electron Microscope Computational Materials Science 2 (1994) 249-260......... 19

253 P. Forsberg and P. Lepoutre, ESEM Examination of Paper In High Moisture Environment: SurfaceStructural Changes and Electron Beam Damage. Scanning Microscopy 8 (1).......................................... 19

254 P. Forsberg and P. Lepoutre, ESEM Examination of the roughening of paper in high moistureenvironment. Presented at the 1993 PTS Symposium in Munich, Germany................................................ 19

255 L. Mott, S.M. Shaler, L.H. Groom, The Tensile Testing of Individual Wood Fibers Using EnvironmentalScanning Electron Microscopy and Video Image Analysis. Submitted to TAPPI Journal ......................... 20

256 G.D. Danilatos, Introduction to the ESEM, Instrument Microscopy Research and Vol. 25, #5&6 ............ 20

256 R.E. De La Para, A Method to Detect Variations in the Wetting Properties of Microporous PolymerMembranes. Microscopy Research and Technique 25:362-373 (1993) ........................................................ 20

257 P. Messier and M. Vitale, Cracking in Albumen Photographs: An ESEM Investigation. MicroscopyResearch and Technique 25:374-383............................................................................................................ 21

258 J.H. Rask, J.E. Flood, J.K. Borchardt, and G.A. York The ESEM Used to Image Crystalline Structures ofPolymers and to Image Ink on Paper. Microscopy Research and Technique 25:384-392. ........................ 21

259 S.P. Collins, R.K. Pope, R.W. Scheetz, R.I Ray, P.A. Wagner, B.J. Little Advantages of EnvironmentalScanning Electron Microscopy in Studies of Micro organisms. Microscopy Research and Technique25:398-405 .................................................................................................................................................. 21

260 L.M. Egerton-Warburton, B.J. Griffin, and J. Kuo Microanalytical studies of Metal Localization inBiological Tissues by Environmental SEM. Microscopy Research and Technique 25:406-411 ................ 22

261 P.J.R. Uwins, M. Murray, and R.J. Gould Effects of Four Different Processing Techniques on theMicrostructure of Potatoes: Comparison with Fresh Samples in the ESEM Microscopy Research andTechnique 25:413-418 ................................................................................................................................. 22

262 L.C. Gilbert and R.E. Doherty, Using ESEM and SEM to compare the Performance of Dentinconditioners Microscopy Research and Technique 25:419-423................................................................... 22

263 S.L. Geiger, T.J. Ross, and L.L. Barton Environmental Scanning electron Microscope (ESEM Evaluationof Crystal and Plaque Formation Associated with Biocorrosion Microscopy Research and Technique25:429-433 .................................................................................................................................................. 22



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264 L.F. Keyser and Ming-Taun Leu, Morphology of Nitric Acid and Water Ice Films Microscopy Researchand Technique 25:434-438 .......................................................................................................................... 23

265 H.E. Nuttall and R. Kale, Application of ESEM to Environmental Colloids Microscopy Research andTechnique 25:439-446 ................................................................................................................................. 23

266 Hyung-Min Choi and J.P. Moreau, Oil Sorption Behavior of Various Sorbents Studied by SorptionCapacity Measurement and Environmental Scanning Electron Microscopy Microscopy Research andTechnique 25:447-455 ................................................................................................................................. 23

267 Chao Lung Hwang, Ming Liang Wang, and Shuke Miao Proposed Healing and Consolidation Mechanismsof Rock Salt Revealed by ESEM Microscopy Research and Technique 25:456-464 .................................. 24

268 P.J.R. Uwins, J.C. Baker, and I.D.R. Mackinnon Imaging Fluid/Solid Interactions in HydrocarbonReservoir Rocks Microscopy Research and Technique 25:465-473 ........................................................... 24

269 P.W. Brown, J.R. Hellmann, and M. Klimkiewicz, Examples of Evolution of Microstructure in Ceramicsand Composites Microscopy Research and Technique 25:474-486 ............................................................. 24

270 E.R. Prack, An Introduction to Process Visualization Capabilities and Considerations in theEnvironmental Scanning Electron Microscope (ESEM) Microscopy Research and Technique 25:487-49225

271 N. Koopman, Application of ESEM to Fluxless Soldering Microscopy Research and Techniques 25:493-502 .............................................................................................................................................................. 25

272 K.W. Kirchner, G.K. Lucey, and J. Geis, Copper/Solder Inter-metallic Growth Studies MicroscopyResearch and Techniques 25:503-508 .......................................................................................................... 26

273 T.J. Singler, J.A. Clum, and E.R. Prack, Dynamics of Soldering Reactions: Microscopic ObservationsMicroscopy Research and Technique 25:509-517......................................................................................... 26

274 L.F. Link, W.R. Gerristead, JR., and S. Tamhankar, Copper Thick Film Sintering Studies in anEnvironmental Scanning Electron Microscope Microscopy Research and Technique 25:518-522............ 26

275 W.R. Gerristead, , L.F. Link, R.C. Paciej, P. Damiani, and H. Li, Environmental Scanning ElectronMicroscopy for Dynamic Corrosion Studies of Stainless Steel Piping Used in UHP Gas DistributionSystems Microscopy Research and Technique 25:523-528......................................................................... 27

276 G.D. Danilatos, Bibliography of Environmental Scanning Electron Microscopy Microscopy Research andTechnique 25:529-534 ................................................................................................................................. 27

277 B. Caveny, Cement Hydration Study Using the Environmental Scanning Electron Microscope ICMAProceedings ................................................................................................................................................. 27

278 Robert Pope and Raymond W. Scheetz, Dynamic Events Related to Humidity Changes on BotanicalSamples Imaged with the Environmental SEM, Dept. of Biological Sciences, University of SouthernMississippi, Hattisburg, MS 39406-5018...................................................................................................... 27

279 P.A. Wagner, B.J. Little, R.I. Ray, Investigations of Microbiologically Influenced Corrosion UsingEnvironmental Scanning Electron Microscopy Corrosion ‘92, The National Association of CorrosionEngineers, #185. .......................................................................................................................................... 28

280 P.A. Wagner, B.J. Little, R.I. Ray, Biofilms: An ESEM Evaluation of Artifacts Introduced During SEMPreparation, Naval Oceanographic and Atmospheric Research Laboratory, Stennis Space Center, MS39529-5004 ................................................................................................................................................. 28

281 K.-R. Peters, L.A. Firstein, A. Noz, Environmental SEM and Conventional SEM Imaging of Electron-Sensitive Resist: Contrast Quality and Metrological Applications, Micro electric Engineering 17 (1992)455-458 Elsevier Science Publishers B.V. .................................................................................................... 28



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282 Sudhir Mehta, Richard Jones, Cryogenics with Cement Microscopy Redefines Cement Behavior, ARCOExploration & Production Technology, Oil & Gas Journal, Oct. 3, 1994 ...................................................... 28

283 H.S. Kaufman, K.D. Littlemoe, J.T. Mastovich, H.A. Pitt, Environmental Scanning Electron Microscopy ofFresh Human Gallstones Reveals New Morphologies of Precipitated Calcium Salts. G.W. Bailey, J.Bentley and J.A. Small, Editors, Proc 50th Annual Meeting of the Microbeam Analysis Society and the 19thAnnual Meeting of the Microscopial Society of Canada, EMSA, San Francisco Press, 1992. ....................... 28

284 A. D’Emanuele, J. Kost, J.L. Hill, R. Langer, An Investigation of the Effects of Ultrasound on DegradablePolyanhydride Matrices., American Chemical Society (1992) Macromolecules 25. ................................... 29

285 Wang Peiming, Li Pingjiang, Chen Zhiyuan, Research on the Morphology of Cement Hydrates by SEM,State Key Laboratory of Concrete Materials Research, Tongji University, Shanghai, 200092, China............ 29

286 Bill Caveny, Gant McPherson, Lance Brothers, Sudhir Mehta, Crystal Phases of Cement Paste Cured inHigh Temperature CO2 Environment....................................................................................................... 29

287 S. Mehta, Imaging of Wet Specimens in Their Natural State Using Environmental Scanning ElectronMicroscope (ESEM): Some Examples of Importance to Petroleum Technology. (1991) Society ofPetroleum Engineers Inc. SPE 22864.......................................................................................................... 29

288 A.B.M. Simanjuntak, P.T. Caltex, L.L. Haynes, ESEM Observations Coupled With Coreflood TestsImprove Matrix Acidizing Designs, (1994) Society of Petroleum Engineers Inc. ....................................... 30

289 L.L. Haynes, ESEM: An emerging Technology for Determination of Fluid/Rock Interactions inHydrocarbon Production., (1991) Texaco, EPTM TM# 91-186. ................................................................ 30

290 P.J.R Uwins ESEM: Environmental Scanning Electron Microscopy EIX 95-17 EIX95172606357 NDN -017-0224-8612-8 (1994) Materials Forum v18 p51-75................................................................................. 31

291 J.E. Johnson Microscopy Research and Technique, Volume 25, Numbers 5 and 6, August 1993, WileyLiss, A John Wiley & Sons, Inc., Publication. .............................................................................................. 31

292 Junhui Li; Pecht, M. Engel, P. A.; Chen, W. T., Dynamic investigation of thermal and sorptive effects onelectronic packages -.................................................................................................................................. 33

293 Read, 0. T.; Dally, J. W. EDITOR- Engel, P. A.; Chen, W. T., Local strain measurement by electronbeam moiré -Proceedings of the 1993 ASME International Electronics Packaging Conference New York,NY, USA).................................................................................................................................................... 33

294 Bong Mo Park; Su Jin Chung, Optical, electron microscopic, and X-ray topographic studies of ferroicdomains in barium titanate crystals grown from high-temperature solution -Journal of the AmericanCeramic Society (USA) VOL. 77 NO. 12 Dec. 1994 PP. 3193-201 31 references) Copyright 1995............... 33

295 V.N.E. Robinson, ,B.W. Robinson , Materials Characterization in a Scanning Electron MicroscopeEnvironmental Cell, Scanning Electron Microscopy, Vol. 1, SEM Inc., AMF O’Hare IL 60666, USA . .... 33

296 P.T. Miller, S.A. Farrington, L. Kovach, Petrographic Thin-section and Scanning Electron MicroscopeAnalysis of a Mortar Fabricated in a Microgravity Environment: Preliminary Studies., Master BuildersInc. .............................................................................................................................................................. 33

297 U. Landman, R. Nieminen, Computational Materials Science, Volume 2, No. 2, March 1994, Commat 2 (2)213-412 (1994).Elsevier, ISSN 0927-0256................................................................................................... 34

297a A. Mahmoudi, B. Soudini, N. Amrane, B. Khelifa and H. Aourag Conduction bond edges charge densitiesin Cdx Zn1-x S. ............................................................................................................................................. 34

297b J. Kohanoff Phonon spectra from short non-thermally equilibrated molecular dynamics simulations ... 34

297c D. Bourbie and K. Driss-Khodia Transport of electronic excitations in disordered systems..................... 34



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297d J. Hutter, H.P. Lothi and M. Parrinello Electronic structure optimization in plane-wave-based densityfunctional calculations by direct inversion in the iterative subspace ....................................................... 34

297e Y. Xi, T.B. Bergstrom and H.M. Jennings Image intensity matching technique: Application to theenvironmental scanning electron micro-scope .......................................................................................... 34

297f K. Kokko, P.T. Salo and K. Mansikka First principles study of the solute atom induced lattice distortioneffects on bulk modulus and band structure in Li-alloys .......................................................................... 34

297g A. Fischer and A. Pyzalla-Schieck Calculation of thermal micro residual stresses in materials containingcoarse hard phases ..................................................................................................................................... 34

297h D. Faken and H. Johnsson Systematic analysis of local atomic structure combined with 3D computergraphics...................................................................................................................................................... 34

297i M. Driz, N. Bodi, B. Soudini, N. Amrane, H. Abid, N. Bouarissa, B. Khelifa and H. Aourag The alloyingand pressure dependence of band gaps in GaAs and GoAsxP1-x ............................................................... 34

297j M. Sluiter Introducing distant interactions in the cluster variation method............................................. 34

297k Chen Haoran, Yang Quangsan and F.W. Williams A self-consistent finite element approach to theinclusion problem....................................................................................................................................... 34

297l M.J.W. Greuter and L. Niesen Molecular dynamics simulation of the lattice dynamics of solid Kr.......... 34

297m V. Vydra, K.M.A. El-Kader and V. Ch6b Influence of variations of temporal pulse shape in excimerlaser processing of semiconductors............................................................................................................ 34

297n L.-W. Wang and A. Zunger Large scale electronic structure calculations using the Lanczos method..... 34

297o C.S. Wu and L. Dorn Computer simulation of fluid dynamics and heat transfer in full-penetrated TIGweld pools with surface depression............................................................................................................ 34

297p P.H. Lambin, L. Philippe, J.C. Charlier and J.P. Michenaud Electronic band structure of multilayeredcarbon tubules............................................................................................................................................ 35

297q H.-J. Unger Theory of vacuum tunneling and its application to the scanning tunneling microscope ...... 35

297r H. Nara, T. Kobayasi, K. Takegahara, M.J. Cooper and D.N. Timms Optimal number of directions inreconstructing 3D momentum densities from Compton profiles of semiconductors ................................ 35

297s G. Tichy Interaction potentials in metals................................................................................................... 35

297t J. Kudrnovski, V. Drchal, S.K. Bose, 1. Turek, P. Weinberger and A. Posturel Electronic properties ofrandom surfaces......................................................................................................................................... 35

297u A. Qteish, R.J. Needs and V. Heine Polarization, structural and electronic properties of SiC polytypes. 35

297v A. Qteish and R.J. Needs Ab-initio pseudo potential calculations of the valence band offset atHgTe/CdTe, HgTe/InSb and CdTe/InSb interfaces: transitivity and orientation dependence ............... 35

297w A. Muhoz and K. Kunc New phases and physical properties of the semiconducting nitrides: AIN, GaN,InN.............................................................................................................................................................. 35

298 V. N. E. Robinson, The SEM Examination of Wet Specimens, SCANNING Vol. 1, 149-156 (1978), G.Witzstrock Publishing House Inc., Received: July 24, 1978, Faculty of Applied Science, The University ofNew South Wales, P. 0. Box 1, Kensington, N.S.W., 2033, Australia........................................................... 35

299 V.N.E. Robinson , Facility of Applied Science, University, of New South Wales, PO Box 1, Kensington, N.S.W., 2033, Australia, A simple technique for examining frozen hydrated specimens in the scanningelectron microscope, Journal of Microscopy, Vol. 104, Pt 3, August 1975, pp. 287-292.............................. 36



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300 V.N.E. Robinson , Facility of Applied Science, University, of New South Wales, PO Box 1, Kensington, N.S.W., 2033, Australia, A wet stage modification to a scanning electron microscope, Journal of Microscopy,Vol. 103, Pt 1, January 1975, pp. 71-77. ...................................................................................................... 36

301 Todd Bruce Bergstrom, An Environmental Scanning Electron Microscope (ESEM) Investigation ofDrying Cement Paste: Drying Shrinkage, Image Analysis, and Modeling. Northwester University,Evanston IL, USA, December 1993, © 1993 T.B. Bergstrom ....................................................................... 36

302 R.E. Cameron and A.M. Donald, Minimizing Sample Evaporation In the Environmental ScanningElectron Microscope, Polymers and Colloids Group, Cavendish laboratory, Madingley Road, Cambridge,CB3 OHE, United Kingdom ........................................................................................................................ 36

303 R.E. Cameron, University of Cambridge, Dept. of Materials Science and Metallurgy, Environmental SEM:Principles and Applications, Microscopy & Analysis , May 1994............................................................... 37

304 N. Baumgarten, Environmental SEM Premieres, Nature Vol., 341, No. 6237, pp. 81-82 7th September, 1989© Macmillian Magazines Ltd. 1989............................................................................................................. 37

305 R. Mulvaney, E.W. Wolff, K. Oates, Sulfuric acid at grain boundaries in Antarctic ice. Nature Vol. 331,No. 6153, pp. 247-249, 21 January 1988 © Macmillian Magazines ltd., 1988.............................................. 37

306 Leon F. Keyser, Ming-Taun Leu, Surface Areas And Porosities Of Ices Used To Simulate StratosphericClouds. Earth and Space Sciences Division Jet Propulsion Laboratory, California Institute of Technology,Pasadena, CA 91109.................................................................................................................................... 37

307 Timothy J. Singler, James A. Clum, Dept. of Mechanical Engineering State University of New York atBinghamton, Edward Prack, Corporate Manufacturing Research Center, Motorola Inc., Schaumburg, IL60196, Microscopic Observations of Solder-Substrate Interactions. ....................................................... 38

308 H.S. Betrabet, J.K. McKinlay and S.B. McGee, Dynamic Observations of Sn-Pb Solder Reflow in aHotstage Environmental Scanning Electron Microscope, Philips Laboratories Briarcliff, © NorthAmerican Philips Corporation, 1991, Document No. MS 91-021 ................................................................. 38

309 John G. Sheehan, L.E. Scriven, Assessment of Environmental Scanning Electron Microscopy for CoatingResearch, Dept. of Chemical Engineering and Materials Science, University of Minnesota. 1991 CoatingConference. ................................................................................................................................................. 38

310 P. Forsberg, P. Lepoutre, Degradation of Pulp Papers Under Electron Beam, University of Maine, Dept. ofChemical Engineering, Jenness Hall, Orono Maine 04469, Submitted to Nordic Pulp and Paper ResearchJournal......................................................................................................................................................... 39

311 P. Forsberg, P. Lepoutre, A New Insight into the Fiber-rising Phenomena, University of Maine, Dept. ofChemical Engineering, Jenness Hall, Orono Maine 04469, Nordic Pulp and Paper Research Journal No.3/1992. ........................................................................................................................................................ 39

312 H.C. Greenblatt, M. Dombroski, W. Klishevich, J. Kirkpatrick, I. Bajwa, W. Garrison, B.K. Redding,Encapsulation and Controlled Release of Flavours and Fragrances, Royal Society of Chemistry, 1993V:138, pp. 148-1963 .................................................................................................................................... 39

313 Brendon J. Griffin, Rachael L. Trautman, Jeanette Coffey, X-ray Resolution at Low Chamber Pressures andChamber Gas Fluorescence in the ElectroScan ESEM. Center for Microscopy and Microanalysis, TheUniversity of Western Australia., Nedlands, W.A. Australia 6009................................................................ 39

314 C.E. Kalnas, J.F. Mansfield, G.S. Was, J.W. Jones, An in-situ bend fixture for deformation and fracturestudies in the Environmental Scanning Electron Microscope., Materials Science and EngineeringDepartment, University of Michigan, Ann arbor, MI 48109. ....................................................................... 39



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315 Po-Fu Huang, Barbara J. Turpin, Mike J Pipho, David B. Kittleson, Peter H. McMurry, Cloud Processing ofDiesel Chain Agglomerates, for submission to Journal of Aerosol Science, Particle Technology Laboratory,University of Minnesota, Minneapolis, MN 55455 Publication Number 875, August 1993.......................... 40

316 Mehta, S. . Jones, R., Chatterji, J.. and McPherson, G. Effects of amorphous and crystalline silica onphase chemistry, microstructure and strength of set cement at elevated temperatures., ARCOExploration and Production Technology, Plano, Texas 75075, Halliburton Energy Services, Duncan,Oklahoma 73533 ......................................................................................................................................... 40

317 Roger B. Bolon, Craig Robertson, X-RAY & MICROSTRUCTURAL E-SEM ANALYSIS OFREACTIONS AND NONCONDUCTING MATERIALS IN GASEOUS ENVIRONMENTS., GECorporate Research & Development, Schenectady, NY 12301 ..................................................................... 41

318 D.A. Lange, Sujata, K., and H.M. Jennings, CHARACTERIZATION OF CEMENT-WATER SYSTEMS,Northwestern University, Evanston, IL ........................................................................................................ 41

319 Hoyberg, K.; Knaggs, H., Environmental scanning electron microscopy of microcomedones - Proceedings- Annual Meeting, Microscopy Society of America 1994.. p 370-371 1994 .................................................. 41

320 Forsberg, Paivi; Lepoutre, Pierre, ESEM estimation of the roughening of paper in high moistureenvironment -Proceedings of the International Printing and Graphic Arts Conference, 1994. TAPPI Press,Atlanta, GA, USA. p 229-236 1994Univ. of Maine, Orono, ME, USA Proceedings of the InternationalPrinting and Graphic Arts Conference - Halifax, Canada. Proceedings of the International Printing andGraphic Arts Conference ............................................................................................................................. 41

321 Meredith, P., Donald, A.M., Luke, K. Pre-induction and induction hydration of tricalcium silicate: anenvironmental scanning electron microscopy study. Journal of Materials Science V30 N8 Apr. 15, 1995. p1921-1930 ................................................................................................................................................... 42

322 Belenii, I.; Ebrahimi, M.; Hascicek, Y. S. Study of thermal expansion of Bi-2212/Ag tape conductors usingESEM - INS Physica C (Netherlands) VOL. 247 NO. 3-4 1 June 1995 PP. 371-5 12 reference(s) ISSN-0921-4534 CODENPHYCE6, - Nat. High Magnetic Field Lab., Tallahassee, FL, USA COPYRIGHT OFBIBLIOGRAPHIC- Copyright 1995, FIZ Karlsruhe..................................................................................... 42

323 Gergova, Katia; Eser, Semih; Schobert, Harold H.; Klimkiewicz, Maria ;Brown, Paul W. Environmentalscanning electron microscopy of activated carbon production from anthracite by one-step pyrolysis-activation - EIX 95-37 EIX95372798448 NDN- 017-0234-8363-9 Fuel v 74 n 7 Jul 1995. p 1042-1048 1995Article ISSN-0016-2361 CODEN-FUELAC AUTHOR AFFILIATION-Pennsylvania State Univ, UniversityPark, PA, USA............................................................................................................................................. 42

324 Albert Folch, Javier Tejada, Christopher H. Peters , Mark S. Wrighton, Electron beam deposition of goldnanostructures in a reactive environment, 2080 Appl. Phys. Lett. 66 (16), 17 April 1995 0003-6951/95/66(16)/2080/3/$6.00 (D 1995 American Institute of Physics........................................................... 43

325 Abe, T., Ohmori, ., Nikaido, H., Kimura, H., Ozawa, M., Kinbara, ., 1992, Influence of ion beam irradiationon the structure and properties of dielectric thin films], Journal of the Vacuum Society of Japan, 35, 9,773-80 ......................................................................................................................................................... 43

326 Bower, N.W., Stulik, D.C., Doehne, E., D 1994, A critical evaluation of the Environmental ScanningElectron Microscope for the analysis of paint fragments in art conservation, J Fresenius J Anal Chem., 348,5-6, 402-410, F .ih ...................................................................................................................................... 43

327 Chen, J., Brooks, K.G. Udayakumar, K.R., Cross, L.E., D 1991, Crystallization dynamics and rapidthermal processing of PZT thin films, J Ferroelectric Thin Films II Symposium, E Edited by: Kingon, A.I ,E Edited by: Myers, E.R, E Edited by: Tuttle, B, I Mater. Res. Soc, C Boston, MA, USA, P 33-8, SFerroelectric Thin Films II Symposium........................................................................................................ 43



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328 Danilatos, G.D., D 1990, Equations of charge distribution in the environmental scanning electronmicroscope (ESEM) J Scanning Microscopy V 4 N 4 P 799-823 ................................................................ 44

329 Danilatos, G.D., D 1990, Mechanisms of detection and imaging in the ESEM, Journal of Microscopym V1, P 9-19,..................................................................................................................................................... 44

330 Doehne, E., Stulik, D.C., D 1990, Applications of the environmental scanning electron microscope toconservation science, Scanning Microscopy, V 4, N 2, P 275-86 ................................................................ 44

331 Doehne, Eric Stulik, Dusan 1991, Dynamic studies of materials using the environmental scanningelectron microscope, Materials Research Society, 9800 McKnight Rd., Suite 327, Pittsburgh, P 31-38....... 44

332 Doehne, E., Bower, N., D 1993 Empirical evaluation of the electron skirt in the environmental SEM:Implications for energy dispersive X-ray analysis, Microbeam Analysis, V 2, supplement, P S35-36 ....... 44

333 Doehne, E.,Bower, N., D 1993, Experimental conditions for semi-quantitative SEM/EDS of painting, crosssections using the environmental scanning electron microscope, Microbeam Analysis, V 2, supplement, PS39-40 ......................................................................................................................................................... 45

334 Doehne, E., D 1994, In situ dynamics of sodium sulfate hydration and dehydration in stone pores:Observations at high magnification using the environmental scanning electron microscope, IIIInternational Symposium on the Conservation of Monuments in the Mediterranean Basin, E Fassina, V. EOtt, H., E Zezza, F., Soprintendenza ai Beni Artistici e Storici di Venezia, C Venice, Italy, P 143-150, InEnglish ........................................................................................................................................................ 45

335 Farley, A.N., Shah, J.S., D 1990, Primary considerations for image enhancement in high-pressurescanning electron microscopy. 1. Electron beam scattering and contrast, Journal of Microscopy, V 3 , P 379-88 ................................................................................................................................................................ 45

336 Fujimaki, N., Kano, Y., Ishikawa, H., Ohmori, A., Kawata, S., D 1990, Some Observations on Mouse-Tissues with the Environmental Scanning Electron-Microscope (ESEM), Journal of Electron Microscopy,V 39, N 4, P 299-299 ................................................................................................................................... 45

337 Huang, Po-Fu, Turpin, B.J., Pipho, M.J., Kittelson, D.B., McMurry, P.H., 1994, Effects of watercondensation and evaporation on diesel chain-agglomerate morphology, Journal of Aerosol Science, V 25,N 3, P 447-59 .............................................................................................................................................. 45

338 Kawata, S., D 1991, [Environmental scanning electron microscope], Journal of the Japan Society ofPrecision Engineering, 57, N 7, 1178-81...................................................................................................... 45

339 Kodaka, T., Debari, K., Sato, T., Tada, T., D 1991, The Environmental Scanning Electron-Microscope(ESEM) Observation of Human Dentin, Electron Microsc, 40 4, P 267-267, Journal Article .................... 46

340 Kodaka, T., Toko, T., Debari, K., Hisamitsu, H., Ohmori, A., Kawata, S. D 1992, Application of theEnvironmental SEM in Human Dentin Bleached With Hydrogen Peroxide Invitro, Journal of ElectronMicroscopy, V 41, N 5, P 381-386 ............................................................................................................... 46

341 Kozuka, Y., Nakamura, A., Futaesaku, Y., Inoue, S., D 1991, Dynamic Observations of ParticulatedSpecimens Under ESEM - a Model Experiment Using Cryptomeria-Japonica Pollen Grain, ElectronMicrosc., V 40, N 3, P 204-204.................................................................................................................... 46

342 McDonough, C., Gomez, M.H., Lee, J.K., Waniska, R.D., Rooney, L.W., D 1993, Environmental scanningelectron microscopy evaluation of tortilla chip microstructure during deep-fat frying, Journal of FoodScience, V 58, N 1, P 199-213 ..................................................................................................................... 46

343 Rodriguez, M.A., Chen, Bin-Jiang,, Snyder, R.L., D 1992, The formation mechanism of texturedYB2Cu3O7-?, Physica C, 195, N 1-2, P 185-94 .......................................................................................... 46



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344 Sarkar, S.L., Xu,.M. D 1992, Preliminary Study of Very Early Hydration of Superplasticized C3A+,Gypsum by Environmental SEM, Cement and Concrete Research, V 22 N 4, P 605-608, F .ih ................ 46

345 Sayer, M., Nolan, P., Hansson, C.M., D 1993, Scanning Electron Microscopy Without Pain - theEnvironmental SEM, Canadian Ceramics Quarterly-Journal of the Canadian Ceramic Society, V 62, N 2, P104-105 Reprint: QUEENS UNIV,DEPT MAT & MET ENGN KINGSTON K7L 3N6, ONTARIOCANADA.................................................................................................................................................... 47

346 Stulik, Dusan, Doehne, Eric, D 1991, Applications of environmental scanning electron microscopy in artconservation and archaeology, Materials Research Society, 9800 McKnight Rd., Suite 327, Pittsburgh, V185, P 23-30, ............................................................................................................................................... 47

347 Thaveeprungsriporn, V., Mansfield, J.F., Was, G.S., D 1994 Development of an economical electronbackscattering diffraction system for an environmental scanning electron microscope, Journal of MaterialsResearch, V 9, N 7, P 1887-94 ..................................................................................................................... 47

Dept. of Nucl. Eng., Michigan Univ., Ann Arbor, MI, USA, July 1994, vol.9, no.7 348 Wight, S.A., Zeissler,C.J., D 1993, Environmental Scanning Electron Microscope Imaging Examples Related to ParticleAnalysis, Microscopy Research and Technique, V 25, N 5-6, P 393-397 ..................................................... 47

Reprint: NATL. INST. STAND & TECHNOL. BLDG. 222,RM A113 GAITHERSBURG, MD USA 208995-6 349 Yamaguchi, T., Yanao, Y., D 1990, Environmental Scanning Electron-Microscope, Journal ofElectron Microscopy, V 39, N 4, P 284-284 ................................................................................................. 47

350 Yamaguchi, T., Kawata, S., Suzuki, S., Sato, T., A Sato, Yu, D 1993, New linewidth measurement systemusing environmental scanning electron microscope technology, 6th International MicroProcessConference, C Hiroshima, Japan, P 6277-80, S Japanese Journal of Applied Physics, Part 1 (Regular Papers& Short Notes)............................................................................................................................................. 47

351 Cameron, R. E., Donald, A. M., Journal of Microscopy, March 1994, Minimizing sample evaporation inthe environmental scanning electron microscope, P 227-237. .................................................................. 48

352 Danilatos, G. D., XII International Congress for Electron Microscopy, D 1990, P. 372-373, Detection byInduction in the Environmental SEM........................................................................................................... 48

353 Danilatos, G.D., Journal of Microscopy, Mechanisms of detection and imaging in the ESEM, V 160,October 1990, P 9-19.................................................................................................................................. 48

354 Mehta, S., Jones, R., Caveny, B., Chatterji, J. McPherson, G. Environmental Scanning ElectronMicroscope (ESEM) examination of Individually hydrated Portland cement phases.............................. 48

355 Harner, A.L., Copeland, C.H., Grim, B.G., Destruction of Concrete By Fertilizers-Urea Ammonium Nitratevs Concrete, National Fertilizer and Environmental Research Center, Tennessee Valley Authority,Muscle Shoals, Alabama ............................................................................................................................ 49

356 Caveny, B., McPherson, G., Brothers, L., Mehta, S., Crystal Phases of Cement Paste Cured in HighTemperature--CO2 Environment.............................................................................................................. 49

357 Miller, P.T., Farrington, S.A., Kovach, L., Petrographic Thin Section and Scanning ElectronMicroscope Analysis of a Mortar Fabricated in a Microgravity Environment: Preliminary Studies..... 49

358 Mehta, S., Jones, R. Chatterji, J. McPherson, G., Effects of amorphous and crystalline silica on phasechemistry, microstructure and strength of set cement at elevated temperatures. ................................... 50

359 Peiming, W., Pingjiang, L. Zhiyuan, C., Research on the morphology of cement hydrates by SEM. ...... 50

360 Damidot, D., Sorrentino, F., Observation of the hydration of cement paste by ESEM: Care needed tostudy the early hydration, St. Quentin, Fallavier Cedex, France............................................................. 50



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361 Danilatos, G.D., Postle, R., The Time Temperature Dependence of the Complex Modulus of Keratin Fibers,Journal of Applied Polymer Science, V. 28, P. 1221-1234, D. 1983.......................................................... 50

362 Danilatos, G.D., Postle, R., Dynamic Mechanical Properties of Keratin Fibers During Water Absorption andDesorption, Journal of Applied Polymer Science, V. 26, P. 193-200, D. 1981........................................... 50

363 Danilatos, G.D., Postle, R., Low Strain Dynamic Mechanical Properties of Keratin Fibers During WaterAbsorption, J. Macromol. Sci. Phys., B 19 (1) P. 153-165 (1981). ............................................................ 51

364 Doehne, E., Stulik, D.C., Applications of the Environmental Scanning Electron Microscope toConservation Science, Scanning Microscopy, V. 4, N. 2, D. 1990, P. 275-286.......................................... 51

365 Bergstrom, T.B., Jennings, H.M., The Formation of Bonds in Tricalcium Silicate Pastes as Observed byScanning Electron Microscopy, Journal of Materials Science Letters II, D. 1992, P. 1620-1622. .......... 51

366 Meredith, P., Donald, A.M., Luke, K., Pre-Induction and Induction Hydration of Tricalcium Silicate:An Environmental Scanning Electron Microscopy Study, Cavendish Laboratory, Cambridge,University Physics ...................................................................................................................................... 51

367 Sujata, K., Jennings, H.M., Formation of a Protective Layer During the Hydration of Cement, Journal ofAmerican Ceramics Society, D. 1992, M. 196122. .................................................................................... 52

368 Lange, D.A., Sujata, K., Jennings, H.M., Observations of Wet Cement Using Electron Microscopy,Ultramicroscopy, V. 37, D. 1991. P. 234-238............................................................................................. 52

369 Derbin, G.M., Palsson, B.O., Mansfield, J.F., Wheatley, T.A., Dressman, J.B., Release Behavior fromEthylcellulose-Coated Pellets: Thermomechanical and Electron Microbeam Studies, PharmaceuticalTechnology, D. 1996, P. 70-81.................................................................................................................... 52

370 Carpenter, D.T., Smith, D.A., Lloyd, J.R., Observation of Passivated A1-1% Cu Lines Using EnvironmentalScanning Electron Microscopy (ESEM), Department of Materials Science and Engineering, LehighUniversity, Bethlehem, PA 18018. ............................................................................................................ 52

371 Roberts, R.A., Shukla, A.J., Rice, T., Characterization of Polyox® Granules using Environmental ScanningElectron Microscopy, Dept. of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee,Memphis, TN 38163, Philips ElectroScan, Wilmington, MA 01887....................................................... 53

372 Pesenti, F., Hassler, J.C., Lepoutre, P., Influence of Pigment Morphology on Microstructure and Gloss ofModel Coatings, Paper Surface Science Program, Dept. of Chemical Engineering, University of Maine,53

373 Stanislawska, A., Lepoutre, P., Consolidation of Pigmented Coatings: Development of Porous Structure,Tappi Journal, V. 79, N. 5. ........................................................................................................................ 53

374 Shaler, S.M., Groom, L., Mott, L., Microscopic Analysis of Wood Fibers using ESEM and ConfocalMicroscopy, Wood Science and Technology, University of Maine, Oroni, ME, Southerin Forest Expt.Sta., USDA Forest Service, Pineville, LA, Dept. of Forest Management, University of Maine, Orono,ME.............................................................................................................................................................. 54

375 Mott, L, Shaler, S.M., Groom, L.H., A Technique to Measure Strain Distributions in Single Wood PulpFibers, Wood and Fiber Science, 28 (4) 1996, P. 429-437.......................................................................... 54

376 Dickson, R.J., LePoutre, P., Macro-and Micro-Mechanical Interlocking in Coating-Paper/BoardAdhesion..................................................................................................................................................... 54

377 Wight, Scott; Gillen, Greg and Herne, Tonya (1997) “Development of Environmental ScanningElectron Microscopy Electron Beam Profile Imaging with Self-Assembled Monolayers and SecondaryIon Mass Spectroscopy”, Scanning 19, 71-74. ........................................................................................... 55

378 Doehne, Eric (1997) “A New Correction Method for high-Resolution Energy-Dispersive X-RayAnalyses in the Environmeental Scanning Electron Microscope”, Scanning 19, 75-78........................... 55



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379 Schnarr, Holger and Füting, Manfred W. (1997) “Some Aspects of Optimizing Contrasts for theInvestigation of Joint Materials in the Environmental Scanning Electron Microscope”, Scanning 19, 79-84. ............................................................................................................................................................... 55

380 Carlton, Robert A. (1997) “The Effect of Some Instrument Operating Conditions on the X-RayMicroanalysis of Particles in the Environmental Scanning Electron Microscope”, Scanning 19, 85-91. 56

381 Jenkins, L. M. and Donald, A. M. (1997) “Use of the Environmental Scanning Electron Microscope forthe Observation of the Swelling Behavior of Cellulosic Fibres”, Scanning 19, 92-97. ............................. 56

382 Ray, Richard; Little, Brenda; Wagner, Patricia and Hart, Kevin (1997) “Environmental ScanningElectron Microscopy Investigations of Biodeterioration”, Scanning 19, 98-103. ..................................... 56

383 Roberts, R.A.; Shukla, A.J. and Rice, T. (1997) “Characterization of Polyox® Granules UsingEnvironmental Scanning Electron Microscopy”, Scanning 19, 104-108. ................................................. 57

384 Hoyberg, Karen (1997) “Environmental Scanning Electron Microscopy of Personal and HouseholdProducts”, Scanning 19, 109-113. .............................................................................................................. 57

385 Yeh, C. L.; Kuo, K. K.; Klimkiewicz, M. and Brown, P. W. (1997) “Environmental Scanning ElectronMicroscopy Studies of Diffusion Mechanism of Boron Particle Combustion” , Scanning 19, 114-118... 57

386 Foitzik, Andreas H.; Füting, Manfred W.; Hillrichs, Georg and Herbst, Ludolf-Johannes (1997) “InSitu Laser Heating in an Environmental Scanning Electron Microscope”, Scanning 19, 119-124. ........ 57

387 Wight, Scott A. (1997) “Better Visualization Inside the Environmental Scanning Electron Microscopethrough the Infrared Chamberscope Coupled with a Mirror”, Scanning 19, 125-126. ........................... 58

388 Meredith, P.; Donald, A. M. and Thiel, B. (1996) “Electron-Gas Interactions in the EnvironmentalScanning Electron Microscopes Gaseous Detector”, Scanning 18, 467-473............................................. 58

389 Newbury, Dale E. (1996) “Imaging Deep Holes in Structures with Gaseous Secondary ElectronDetection in the Environmental Scanning Electron Microscope”, Scanning 18, 474-482........................ 58

390 Taylor, M. E. and Wight, S. A. (1996) “A New Method for Low-Magnification in the EnvironmentalScanning Electron Microscope”, Scanning 18, 483-489............................................................................ 58

391 Paul, B. K. and Klimkiewicz (1996) “Application of an Environmental Scanning Electron Microscopeto Micromechanical Fabrication”, Scanning 18, 490-496. ........................................................................ 59

392 Pirttiaho, Lauri and Blakely, Jack (1996) “Environmental Scanning Electron Microscope Observationsof H2S Attack on the Protective Oxide on an Ni-Fe Alloy”, Scanning 18, 497-499. ................................. 59

393 De Roever, Edmond W. F. and Cosper, David R. (1996) “Fibre Rising and Surface Roughening inLightweight Coated Paper - an Environmental Scanning Electron Microscopy Study”, Scanning 18,500-507. ...................................................................................................................................................... 59

394 Rao, Sudeep M.; Brinker, C. Jeffrey and Ross, Timothy J. (1996) “Environmental Microscopy in StoneConservation”, Scanning 18, 508-514. ....................................................................................................... 60

395 Neubauer, C. M. and Jennings, H. M. (1996) “The Role of the Environmental Scanning ElectronMicroscope in the Investigation of Cement-Based Materials”, Scanning 18, 515-521............................. 60

396 D’Emanuele, Anthony and Gilpin, Christopher (1996) “Applications of the Environmental ScanningElectron Microscope to the Analysis of Pharmaceutical Formulations”, Scanning 18, 522-527. ............ 60

397 Connolly, Jon H.; Chen, Ying and Jellison, Jody (1995) “Environmental Scanning ElectronMicroscopic Observation of the Hyphal Sheath and Mycofibrils in Postia placenta”, Canadian Journalof Microbiology 41, 433-437....................................................................................................................... 61



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398 Connolly, Jon H. and Jellison, Jody (1995) “Calcium translocation, calcium oxalate accumulation, andhyphal sheath morphology in the white-rot fungus Resinicium bicolor”, Canadian Journal of Botony 73,927-936. ...................................................................................................................................................... 61

399 Stanislawska, Anna and Lepoutre, Pierre (1995) “Effect of Pigment Shape, Binder Content andDewatering Conditions on the Consolidationof Pigmented Coatings”, Proceedings of the 22ndWaterborne, High-Solids & Powder Coatings Symposium, New Orleans, LA, 386-395 ......................... 61

400 Stanislawska, Anna and Lepoutre, Pierre (1995) “Development of Porous Structure During Drying ofPigmented Coatings”, Proceedings of the American Chemical Society Division of Polymeric Materials:Science and Engineering, Chicago, IL, 55-56 ........................................................................................... 62

401 Al-Turaif, H.; Unertl, W. N. and Lepoutre, P. (1995) “Effect of pigmentation on the surface chemistryand surface free energy of paper coating binders”, Journal of Adhesion Science and Technology, 9 (7),801-811 ....................................................................................................................................................... 62

402 Dickson, Robert J. “Adhesion and Cohesion in Coated Paper”................................................................ 62

403 Forsberg, P. “Environmental Scanning Electron Microscope (ESEM)”, Surface Analysis of Paper - ed.T. Crunes, 63-68......................................................................................................................................... 62

404 Smith, David A. (1996) “Some Applications of Electron Optical Techniques to Materials forInterconnects”, Scandem ‘96 - Aarhus...................................................................................................... 62

405 Smith, David A.; Small, Martin and Stanis, Carol (1993) “Electron microscopy of the grain structure ofmetal films and lines”, Ultramicroscopy 51, 328-338................................................................................ 62

406 Groom, Leslie H.; Shaler, Stephen M. and Mott, Laurence (1995) “Characterizing Micro- and Macro-Mechanical Properties of Single Wood Fibers”, 1995 International Paper Physics Conference, 13-22.. 63

407 Mott, Laurence; Shaler, Stephen M. and Groom, Leslie H. “Micro-strain distributions and defects insingle wood-pulp fibers”, Department of Forest Management. Forest Products Laboratory, 5755Nutting Hall, University of Maine, Orono, ME 04469-5755 / USDA Forest Service, Southern ResearchStation. 2500 Shreveport Hwy, Pineville, LA 71360 ................................................................................. 63

408 Griffin, Brendan J. (1997) “Field of view and image distortion : A review of low magnification imagingin the environmental and conventional scanning electron microscopes (SEM)”, Microscopy andMicroanalysis, 3 (2), 1193-4....................................................................................................................... 63

409 Thiel, B. L.; Fletcher, A. L. and Donald, A. M. (1997) “Comparison of amplification and imagingbehaviours of several gases in the environmental SEM”, Microscopy and Microanalysis, 3 (2), 1195-6 63

410 Griffin, Brendan J. (1997) “A new mechanism for the imaging of crystal structure in non-conductivematerials: An application of charge-induced contrast in the environmental scanning electronmicroscope (ESEM)”, Microscopy and Microanalysis, 3 (2), 1197-8 ....................................................... 63

411 Bache, I. C.; Thiel, B. L.; Stelmashenko, N. and Donald, A. M. (1997) “Transport of secondaryelectrons through a film of condensed water: Implications for imaging wet samples”, Microscopy andMicroanalysis, 3 (2), 1199-1200 ................................................................................................................. 64

412 Carlton, R. A.; Orton E. and Lyman, C. E. (1997) “Application of ESEM/EDS to pharmaceuticalsynthesis”, Microscopy and Microanalysis, 3 (2), 1201-1202.................................................................... 64

413 Li, M. J. and Taylor, M. E. (1997) “Characterization of contamination effects on polyimide filmfracture using environmental scanning electron microscope”, Microscopy and Microanalysis, 3 (2),1203-4 ......................................................................................................................................................... 64

414 Gilpin, C. J. (1997) “Biological applications of environmental scanning electron microscopy”,Microscopy and Microanalysis, 3 (2), 1205-6............................................................................................ 64



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415 Mansfield, John (1997) “Review of techniques for overcoming XEDS problems in the environmentalscanning electron microscope”, Microscopy and Microanalysis, 3 (2), 1207-8 ........................................ 64

416 Wight, Scott; Gillen, Greg and Herne, Tonya (1997) “Environmental SEM electron damage imaging ofself assembled monolayers with SIMS”, Microscopy and Microanalysis, 3 (2), 1209-10......................... 64

417 Bache, I. C.; Kitching, S.; Thiel, B. L. and Donald, A. M. (1997) “Variations in the probe beambroadening with operating conditions in the ESEM: Monte-Carlo simulations and EDXmeasurements”, Microscopy and Microanalysis, 3 (2), 1211-2................................................................. 64

418 Wight, S. A.; Cavicchi, R. E.; Nystrom, M. J. and DiMeo, F. (1997) “Microhotplate chemical vapordepositioon and in the environmental SEM chamber”, Microscopy and Microanalysis, 3 (2), 603-4..... 64

419 Bache, I. C.; Anderson, V. J.; Jones, R. A. L. and Donald, A. M. (1997) “The observation ofhierarchical structures in biopolymer phase separation: novel ESEM contrast mechanisms”,Microscopy and Microanalysis, 3 (2), 605-6.............................................................................................. 65

420 Mutlu, I. H.; Goddard, R. E. and Hascicek, Y. S. (1997) “ESEM hot stage evaluation of sol-gelinsulation coatings for high field HTS magnets”, Microscopy and Microanalysis, 3 (2), 607-8 .............. 65

421 Thiel, B. L.; Hussein-Ismail, M. R. and Donald, A. M. (1997) “Effects of space charge on ESEM gasamplification”, Microscopy and Microanalysis, 3 (2), 609-10 .................................................................. 65

422 Doehne, Eric (1997) “ESEM and video microscopy studies in stone conservation”, Microscopy andMicroanalysis, 3 (2), 613-4......................................................................................................................... 65



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151 Neil Baumgarten, SEM for imaging specimens in their natural state, American Laboratory June 1990

Key Words: ESEM, natural state

Abstract: The development of an Environmental Scanning Electron Microscope (ESEM) culminates a longpursued effort to observe under high magnification materials and processes in their natural state. This articlesketches this development and cites some current applications.

152 K. Sujata, Hamlin M. Jennings, Advances in Scanning Electron Microscopy, MRS Bulletin, March1991

Key Words:

Abstract: Scanning electron microscopes offer several unique advantages and they have evolved intocomplex integrated instruments that often incorporate several important accessories. Their principle advantagestems from the method of constructing an image from a highly focused electron beam that scans across the surfaceof a specimen. The beam generates backscattered electrons and excites secondary electrons and x-rays in a highlylocalized "spot." These signals can be detected, and the results of the analysis are displayed as a specific intensityon screen at a position that represents the position of the electron spot. As with television image, after a givenperiod information about the entire field of view is displayed on the screen, resulting in a complete image. If thespecimen is thin, the same type of information can be gathered from the transmitted electrons, and a scanningtransmission image is thus constructed.The scanning electron microscope is highly versatile and widely used. The quality of the image is related to itsresolution and contrast, which, in turn depends on the diameter of the focused beam as well as its energy andcurrent. Because electron lenses have inherently high aberrations, the usable aperture angles are much smallerthan in a light microscope and, therefore, the electron beam remains focused over a relatively large distance, givingthese instruments a very large depth of focus.Scanning electron microscopes are versatile in their ability to detect an analyze a lot of information. As a resultmodern versions of these instrument are equipped with a number of detectors. Developments are sometimesrelated to placing the detectors in a geometrically attractive position close to the specimen. Positioning oftenminimizes aberration and increases resolution. It is not possible to design an ideal microscope because of the manycompromises necessary however, certain developments have led to greatly improved microscopes and they arediscussed below.

153 Roger Bolon, C.D. Robertson, Eric Lifshin, The Environmental SEM: A New Way To Look AtInsulators, P.E. Russell, Ed., Microbeam Analysis, 1989 © 1989 San Francisco Press, Inc., USA

Key Words:

Abstract: Scientific and even non-technical literature is filled with thousands of scanning electronmicroscope (SEM) micrographs taken of metals, ceramics, minerals, electronic devices, insects, micro-organisms,and many other types of specimens. This widespread use of the conventional SEM is the result of its ease ofoperation, high resolution, and large depth of field. However, not all samples are suitable for the conditionsimposed by this instrument. For example, insulating specimens have always been something of a challengebecause of surface charges generated by the impinging electron beam must be continually drained away to preventdistortion of the image. In addition, samples that outgas, evaporate, melt or decompose under the conditions ofoperation are generally shunned. To overcome these limitations a new type of SEM or ESEM was developed. Thispaper illustrates a selection of materials applications and special-purpose experiments developed to utilize theunique capabilities of the ESEM.

157 G.D. Danilatos, Journal of Microscopy Review, Vol. 162, Pt.3, June 1991 Received 30 April 1990;revised and accepted 11 July 1990.

Key Words: Environmental Scanning Electron Microscope (ESEM), detector (gaseous), ionization (gaseous),scintillation (gaseous), insulators (specimen), wet specimens, live specimens



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Abstract: The Environmental Scanning Electron Microscope (ESEM) allows the examination of specimensin a gaseous environment. It is based on an integration of efficient differential pumping with a new design ofelectron optics and detection systems. Backscattered, cathodoluminescence and X-ray detectors can be designed tofit and to perform optimally in the ESEM. The secondary electron signal can be detected with the gaseous detectordevice, which is a new multipurpose detector. Insulating, uncoated, wet and generally both treated or untreatedspecimens can be studied.

158 Faith Taylor, Thomas A. Hardt, New Approaches to Ceramic Research Using the EnvironmentalScanning Electron Microscope., ElectroScan Corporation, Wilmington, MA 01887

Key Words: ceramic

Abstract: During the past three decades the scanning electron microscope (SEM) has been used to studyceramic materials at high magnifications; largely to observe microstructure before and after processes, and toperform elemental micro-analysis of material dispersion. Ceramics technology has recently become more diversewith the advent of exciting applications such as ceramic engines and superconductors. As the ceramics industryhas expanded in these new directions, the need for more sophisticated imaging tools has also grown.

159 Klaus-Ruediger Peters, Environmental Cryo-Scanning Electron Microscopy, Proceedings of Scanning,‘91.

Key Words: cryo scanning

Abstract: The Environmental Scanning Electron Microscope (ESEM) (Danilatos, 1983) is widely used forimaging of electrical insulators at high gas pressures (1-20 Torr) because surface charging artifacts can beeliminated and secondary electron contrasts (Peters, 1989) can be used for high resolution microscopy. Thiscondition allows the imaging of water in its liquid (Peters, 1990) as well as frozen state.

160 C.D. Robertson, J. Stein, M.L. Porta, R.B. Bolon, M.E. Grenoble A Study of Silicon Release Coatings,Proceedings of Scanning ‘91.

Key Words: silicone

Abstract: Scanning electron microscopy and environmental scanning electron Microscopy (ESEM) wereused to characterize silicone release coatings on a variety of paper substrates exhibiting different release values.The study showed that the applied coating flows to fill in depressions on rough substrates, leaving thin, easilydamaged layers on the high areas after cure. These defects can change the mechanism of the peel.

161 Roger B. Bolon, ESEM, the Technique and Application to Materials Characterization, Scanning Vol.13, Supplement I, 1991.

Key Words:

Abstract: Scientists have long explored ways to modify the SEM in order to allow the direct examination ofmoist biological specimens without the need to resort to tedious and often damaging dehyration and fixationtechniques.

162 Robert K. Pope and Raymond Scheetz, Colonization Of Copper Surfaces By Sulfate-Reducing BrendaLittle, Patricia Wagner, and Richard Ray, Naval Oceanographic and Atmospheric Research Laboratory,Proceedings of SCANNING 91, 1-93.

Key Words: sulfate-reducing bacteria, copper

Abstract: Environmental scanning electron microscopy (ESEM) and energy dispersive x-ray analysis(EDS) were used to characterize the topography and chemical composition of biofilm/corrosion layers produced bysulfate-reducing bacteria (SRB) on copper surfaces. The thickness, tenacity, and chemical composition of thesulfide layers, as well as the severity of localized corrosion, varied among the alloys and mixed cultures.



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Microorganisms were distributed throughout the copper/nickel/iron-rich surface layers-not on top of these layers assome traditional scanning electron micrographs have indicated.

163 Klaus-Reudiger Peters, David G. Rhodes, Roderike Pohl, Chemical Cryo-stabilization of LipidMonolayers and Bilayers, Scanning Vol. 13, Supplement I, 1991.

Key Words: lipid structures

Abstract: Lipid structures present specific preparation and imaging problems for electron microscopybecause they are very liable in non-aqueous environments and very beam sensitive. We used Langumir films madefrom DPPC or films made from lung surfactant lipid extracts as test models for SEM imaging.

165 S. Mehta, ARCO Oil & Gas Co., SPE Member, Imaging of Wet Specimens in Their Natural StateUsing Environmental Scanning Electron Microscope (ESEM): Some Examples of Importance toPetroleum Technology, SPE 22864, Copyright 1991. Society of Petroleum Engineers Inc.

Key Words: wet reservoir rocks

Abstract: The barrier to imaging wet or oily specimens in their 'native' states in a scanning electronmicroscope (SEM) at high resolution and large depth of focus has been broken by the development of a newmicroscope known as the environmental scanning electron microscope (ESEM). With the new features built intothe ESEM, the need for preparing samples with various specimen-destroying preparation techniques has beeneliminated. For example, wet reservoir rocks can be imaged and analyzed in their 'native' state, without drying,freezing, or coating with a conductive layer, by saturating the ESEM specimen chamber with water vapor (PH20 =-0.46 psi [3.2 kpal at 25°C [77°F] ) during examination. The ESEM also allows dynamic experiments to beperformed in a variety of gases at pressures up to 0.6 psi [4kPa) and temperatures up to 1000°C.

This paper was prepared for presentation at the 66th Annual Technical Conference and Exhibition of the Society of Petroleum Engineers held in

Dallas. TX, October 6-9, 1991.

167 B. Little, P. Wagner, J. F. Mansfield, Microbiologically influenced corrosion of metals and alloys, ©1991 The Institute of Metals and ASM International. International Materials Review, 1991 Vol. 36 No. 6,pp. 253-272.

Key Words: microbiologically influenced corrosion

Abstract: In aquatic environments, microorganisms attach to metals and colonize the surface to formbiofilms producing an environment at the biofilm/metal interface that is radically different from that of the bulkmedium in terms of pH, dissolved oxygen, and organic and inorganic species and leading to electrochemicalreactions that control corrosion rates. The term microbiologically influenced corrosion resulting from the presenceand activities of microorganisms within biofilms at metal surfaces. Microorganisms can accelerate rates of partialreactions in corrosion processes and shift the mechanism for corrosion. Microbiologically influenced corrosion hasreceived increased attention by corrosion scientists and engineers in recent years with the development of surfaceanalytical and electrochemical techniques that can quantify the impact of microbes on electrochemical phenomenaand provide details of corrosion mechanisms. Microbiologically influenced corrosion has been documented formetals exposed to sea water, fresh water, demineralized water, process chemicals, food stuffs, soils aircraft fuels,human plasma, and sewage.

171 K.-R. Peters, L.A. Firstein, A. Noz, Environmental SEM and Conventional SEM Imaging of Electron-Sensitive Resist: Contrast Quality and Metrological Applications, Microelectronic Engineering 17(1992), pp. 455-458, Elsevier.

Key Words: sub-micron IC’s, topographic contrast

Abstract: State-of-the-art SEM metrological approaches are discussed to elucidate inherent deficienciesthat prevent an accurate assessment of image fidelity in the production or inspection of sub-micron IC’s, especially



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on the resist level. The new technique of Environmental SEM is demonstrated to allow topographic contrastgeneration, unaffected by surface charging , for SAL-601.

172 K.-R. Peters, Principles of Low Vacuum Scanning Electron Microscopy, Molecular ImagingLaboratory, Biomolecular Structure Analysis Center, University of Connecticut, Farmington, CT 06030-2017.

Key Words:

Abstract:

173 Anthony D’Emanuele,, Ph.D., ESEM - A New Research Tool In Pharmaceutical Science.

Key Words:

Abstract: Researchers in Manchester University’s department of pharmacy are using the United Kingdom’sonly example of a new research tool which has many applications in the study of materials used in thepharmaceutical studies.

174 Anthony D’Emanuele, Joseph Kost, Jennifer Hill, Robert Langer, An Investigation of the Effects ofUltrasound on Degradable Polyhydride Matrices., © 1992 by the American Chemical Society andReprinted by permission from Macromolecules, 1992, 25.

Key Words:

Abstract: In vitro methodology has been developed to investigate the effects of therapeutic ultrasound onpolymer erosion. Enhancement in the rate of polymer erosion was demonstrated using therapeutically acceptablelevels of ultrasound on a model class of degradable polymers - polyhydranides. It was found that ultrasoundenhances polymer degradation as demonstrated by the enhanced decrease in polymer molecular weight during theinduction period of erosion. Additionally, morphological changes on the surface of ultrasound exposed deviceswere assessed by environmental scanning electron Microscopy and suggested that cavitation may cause themechanical disintegration of the polymer surface.

175 Patricia A. Wagner, Brenda J. Little, Richard I. Ray, Naval Oceanographic and Atmospheric ResearchLaboratory, Joanne Jones-Meehan, Naval Surface Warfare Center, Investigations of MicrobiologicallyInfluenced Corrosion Using Environmental Scanning Electron Microscopy., Corrosion ‘92 TheNACE Annual Conference and Corrosion Show, Paper #185.

Key Words: Microbiologically influenced corrosion, Environmental Scanning Electron Microscope (ESEM),scanning electron microscopy

Abstract: A newly developed environmental scanning electron microscope (ESEM) coupled with an energydispersive X-ray spectrometer (EDS) was used to characterize the topography and chemical composition of wetbiofilms and corrosion products on metal surfaces in addition to spatial relationships between microorganisms,substratum and corrosion layers. Case studies are presented to demonstrate the applicability and advantages ofESEM/EDS technology in the investigation of microbiologically influenced corrosion (MIC) as compared totraditional methods.

176 Patricia A. Wagner, Brenda J. Little, Richard I. Ray, Raymond Scheetz, Robert Pope, Biofilms: an ESEMevaluation of artifacts introduced during SEM preparation., Journal of Industrial Microbiology, 8,1991, pp. 213-222, Elsevier

Key Words: biofilm, scanning electron microscope, Environmental Scanning Electron Microscope (ESEM)

Abstract: Descriptions of biofilms and their elemental compositions based on scanning electronmicrographs and energy dispersive X-ray analysis cannot be related to the original condition of the biofilm on the



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surface. Solvent replacement of water removes extra cellular polymeric material and reduces the concentration ofelements bound within the biofilm. In the wet state, bacteria and micro algae are enmeshed in a gelatinous filmthat is either removed or dried to a thin inconspicuous residue during sample preparation for scanning electronmicroscopy. The Environmental Scanning Electron Microscope (ESEM), provides a fast, accurate image ofbiofilms, their spatial relationship to the substratum and elemental composition.

177 Sudhir Mehta, Environmental Scanning Electron Microscope (ESEM): A New Imaging and AnalysisTechnique of Reservoir Rocks, ARCO, SPE22864, © 1991 SPE Annual Technical Conference in Dallas.

Key Words: reservoir rocks

Abstract: New tools are being developed that allow us to readily explore the structure of porous reservoirrocks and the interaction of fluids with these rocks. The Environmental Scanning Electron Microscope (ESEM),or sometimes called wet SEM, is just such a tool that makes pore level studies easier. The major advantages ofESEM is that the sample does not need to be coated with gold or carbon. This reduces damage to the porestructure and allows liquids to be present in the samples.

178 Howard S. Kaufman*, Keith D. Lillemoe*, John T. Mastovich**, and Henry A. Pitt* *Department ofSurgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland and **Fisons Instruments,Danvers, Massachusetts, Environmental Scanning Electron Microscopy Of Fresh Human GallstonesReveals New Morphologies Of Precipitated Calcium Salts, G.W. Bailey. J. Bentley, and J. A. Small.Editors, Proc. 50th Annual Meeting of the Electron Microscopy Society of America. Held jointly with the27th Annual Meeting of the Microbeam Analysis Society and the 19th Annual Meeting of theMicroscopical Society of Canada/Société de Microscopic du Canada Copyright © 1992 by EMSA.Published by San Francisco Press. Inc.- Box 426800. San Francisco, CA 94142-6800, USA

Key Words: gallstones

Abstract: Gallstones contain precipitated cholesterol, calcium salts, and proteins. Calcium (Ca)bilirubinate, palmitate, phosphate, and carbonate occurring in gallstones have variable morphologies"' butcharacteristic windowless energy dispersive x-ray (EDX) spectra. Previous studies of gallstone microstructure andcomposition using scanning electron microscopy (SEM) with EDX have been limited to dehydrated samples. Inthis state, Ca bilirubinates appear as either glassy masses, which predominate in black pigment stones, or asclusters, which are found mostly in cholesterol gallstones. The three polymorphs of Ca carbonate, calcite, vaterite,and aragonite, have been identified in gallstones by x-ray diffraction,"' however; the morphologies of these crystalsvary in the literature. The purpose of this experiment was to study fresh gallstones by environmental SEM(ESEM) to determine if dehydration affects gallstone Ca salt morphology.

179 Robert J. Koestler, Norman Indictor, and Richard Harneman, Ancient Near Eastern Ivories Imaged andAnalyzed with Environmental Scanning Electron Microscopy and Conventional Scanning ElectronMicroscopy., The Metropolitan Museum of Art, New York, NY and Brooklyn College, CUNY, Brooklyn,NY

Key Words: ivory

Abstract: Two ivory fragments from the Metropolitan Museum of Art’s Ancient Near Eastern ArtDepartment were examined by scanning electron microscopy (SEM): MMA #36.70.12 and MMA #36.70.37J.Each fragment was examined in two types of SEM: a new type - Environmental Scanning Electron Microscope(ESEM ElectroScan Corporation) - which permits microscopy in a near ambient environment (specimens need notbe subjected to high vacuum or surface coating); and conventional SEM (Amray 1600T equivalent).

180 Hemant S. Betrabet, J.K. McKinlay, S.B. McGee, Dynamic Observations of Sn-Pb Solder Reflow in aHotstage Environmental Scanning Electron Microscope.

Key Words: Sn-Pb



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Abstract: Sn-Pb alloys are the most often used solder materials in the microelectronics industry for theinterconnection of components to substrates. The expanded use of surface mount technology has increased theimportance of the mechanical properties of solders. This is because, in addition to providing electrical contacts,the solder functions as structural members by mechanically supporting surface mounted devices on circuit boards.

181 E.R. Prack, C.J. Raleigh, Environmental SEM in the Characterization of Electronics IndustryProcess., Corporate Mfg. Research Center, Motorola Inc., Schaumberburg, Ill 60196

Key Words: solder

Abstract: Environmental Scanning Electron Microscope (ESEM) was used to monitor eutectic tin/leadsolder paste reflow, demonstrating the capability to visualize solder paste reflow which is an important componentattach process for printed circuit boards. The effect of three different atmospheric conditions (air, nitrogen and areducing atmosphere) during reflow were studied. A unique furnace/controller system was used to simulate atypical industrial reflow process. A reducing atmosphere produced the best reflow while lowering the meltingpoint of the solder versus nitrogen or air.

183 J.C. Baker, P.J.R. Uwins, I.D.R. Mackinnon, ESEM Study of Authigenic Chlorite Acid Sensitivity inSandstone Reservoirs, Journal of Petroleum Science and Engineering, March 1992.

Key Words: chlorite acid sensitivity in sandstone reservoirs

Abstract: The effect of HCI on authigenic chlorite in three different sandstone’s has been examined usingan Environmental Scanning Electron Microscope (ESEM), together with conventional analytical techniques. TheESEM enabled chlorites to be directly observed in situ at high magnifications during HCI treatment and wasparticularly effective in allowing the same chlorite areas to be closely compared before and after acid treatment.Chlorites were reacted with 1M to 10M HCI at temperatures up to 80°C and for periods up to 5 months. After alltreatments, chlorites show extensive leaching of iron, magnesium and aluminum, and their crystalline structure isdestroyed. However, despite these major compositional and structural changes, chlorites show little or no visibleevidence of acid attack, with precise morphological detail of individual plates preserved in all samples followingacid treatments. Chlorite dissolution, sensu stricto, does not occur as a result of acidization of the host sandstone’s.Acid-treated chlorites are likely to exist in a structurally weakened state that may make them susceptible tophysical disintegration during fluid flow. Accordingly, fines migration may be a significant engineering problemassociated with the acidization of chlorite-bearing sandstone’s.

184 J.C. Baker, P.J.R. Uwins, I.D.R. Mackinnon, ESEM Study of Illite-smectite freshwater sensitivity insandstone reservoirs, Journal of Petroleum Science and Engineering, June 1992.

Key Words: sandstone reservoirs, illite-smectites

Abstract: The water sensitivity of authigenic smectite- and illite-rich illite-smectites in sandstone reservoirshas been investigated using an Environmental Scanning Electron Microscope (ESEM). The ESEM enabled theillite-smectites to be directly observed in-situ at high magnification during freshwater immersion, and was alsoparticularly effective in allowing the same selected illite-smectite areas to be closely compared before and afterfreshwater treatments.The tendency of authigenic smectite-rich illite-smectite to swell on contact with fresh water varies greatly.Smectite-rich illite-smectite may cosmetically swell to many times its original volume to form a gel which greatlyreduces porosity and permeability, or may undergo only a subtle morphological change which has little or noadverse effect on reservoir quality. Authigenic illite-rich illite-smectite in sandstone’s does not swell whenimmersed in fresh water. Even after prolonged soaking in fresh water, illite-rich illite-smectite particles retaintheir original morphology. Accordingly, illite-rich illite-smectite in sandstone’s is unlikely to cause formationdamage if exposed to fresh water based fluids.

185 H. M. Wallace, P.J.R. Uwins and C. A. McConchiel, Investigation of pollen-stigma interactions inMacadamia and Grevillea using ESEM, Department of Entomology, University of Queensland, St.



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Lucia, Qld 4072, Australia, Electron Microscope Centre, University of Queensland, St. Lucia, Qld 4072,Australia, CSIRO Division of Horticulture, 306 Carmody Rd, St. Lucia, Qld 4067, Australia

Key Words: stigma, pollen, Macadamia, Grevillea, ESEM

Abstract: All members of the plant family Proteaceae are protandrous with the pollen being released priorto the onset of stigma receptivity. In many genera, including Macadamia and Grevillea, the released pollen ispresented at flower opening on a specialized swollen region of the style. The pollen surrounds the receptivestigmatic surface but self pollination is minimized by asynchronous maturation of the pistil and cells that interactwith the pollen. In addition to this temporal and physical separation of the male and female components of flowerdevelopment, a partial self incompatibility mechanism has been reported in some genera (Sedgley et al 1990).After self-pollination in Macadamia, growth of pollen tubes is inhibited in the upper pistil and pollen contents maybe prematurely discharged through a sub-terminal pore in the distorted pollen tube tip (Sedgley, 1983). This selfincompatibility mechanism is thought to limit initial nut set in Macadamia.

186 O'Brien, G.P, Webb, R.I. Uwins P.J.R., Desmarchelier P.M,. Imrie B.C., Suitability Of TheEnvironmental Scanning Electron Microscope For Studies Of Bacteria On Mungbean Seeds,Department of Microbiology, University of Queensland, QLD 4072., Tropical Health Program, Universityof Queensland. Centre for Microscopy and Microanalysis, University of Queensland, CSIRO Division ofTropical Crops and Pastures, Cunningham Laboratory, Qld 4067.

Key Words: foodborne disease, mungbean sprouts

Abstract: There have been several foodborne disease outbreaks associated with the consumption of sproutedseeds (Andrews et al, 1982; O’Mahony et al, 1990; Portney et a!, 1976). In 1988 for example, in Sweden, a largeoutbreak of salmonellosis was associated with the consumption of mungbean sprouts. The imported mungbeanseeds, were found to be contaminated with Salnwnella species (O'Mahoney et al, 1990). Later in the same year,another outbreak of salmonellosis in the United Kingdom was also linked to the consumption of mungbean sprouts.As the origin of the Salmonella in both cases was found to be contaminated seed, a detailed study was initiated toidentify points of attachment and distribution of the bacteria on seeds with different coat types which might revealwhy these bacteria are so resistant to conventional seed treatments (Andrews et al, 1982; Fordham et a4 1975).

187 M.J. Klose, R.I. Webb, D.S. Teakle, Studies on the Association of Tobacco Steak Virus and PollenUsing an Environmental Scanning Electron Microscope (ESEM) and Molecular DistillationTechnique., Department of Microbiology and Centre for Microscopy and Microanalysis, University ofQueensland, QLD 4072.

Key Words: cryofixation, Environmental Scanning Electron Microscope (ESEM), freeze-drying, pollen-bornevirus

Abstract:

200 Danilatos, G.D. , and Robinson, V.N.E. (1979) Principles of scanning electron microscopy at highpressures. Scanning 2:72-82.

Key Words: high pressure, differential pumping, pressure characteristics, PLA, leak rate, apertureconductance, objective aperture, field of view, field distortion, halo, double aperture, wet specimen stability, wool,BSE, water condensation

Abstract: First systematic study of vacuum and pressure characteristics of JEOL JSM-2 SEM. The use of asingle PLA coinciding with objective aperture does not allow short clearance, because of the image distortion andbright halo from the aperture. A double aperture solved the problem. This allowed pressures up to 68.5 mbar with20keV with a modified scintillating BSE detector. The small diameter hole in the detector was used for detectionat the short working distance as opposed to the “hemispherical or wide angle” geometry used Robinson. Wet woolfibers under very stable environmental conditions could be examined at room temperature.



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201 Danilatos, G.D. (1980a) An atmospheric scanning electron microscope (ASEM). Scanning 3:215-217.

Key Words: atmospheric SEM, ASEM, open SEM, high pressure, BSE, acronym ASEM

Abstract: A new detection configuration for the SEM has been devised, which allows the imaging of thesurface of a specimen in the open room, i.e., at atmospheric pressure. Such a device gives rise to a newmicroscope: the Atmospheric Scanning Electron Microscope (ASEM). In this configuration, a backscatteredelectron detector is placed between the pressure limiting aperture and the electron column. The electron beampasses through the final aperture, reaches the sample in the open room and the backscattered electrons passingthrough the same final aperture reach the detector. The principle has been tested and the result reported. The sizeof the aperture used was 22µm. The acronym ASEM has been introduced for the first time.

202 Danilatos, G.D. (1980b) An atmospheric scanning electron microscope (ASEM).Sixth Australian Conference on Electron Microscopy and Cell Biology, Melbourne(18-22 February, 1980), Proc. in Micron 11:335-336.

Key words: atmospheric SEM, open SEM, high pressure, BSE, ESEM, acronym ESEM, acronym ASEM

Abstract: Further advances on the development of ASEM and ESEM are reported. The acronym ESEMhas been introduced for the first time. These two terms correspond to two different configurations, both of whichallow the examination of specimens at any pressure up to one atmosphere. In ASEM the detector is placed abovethe PLA, whereas in ESEM the detector is placed below or is contiguous or integral with PLA. First time two-stage differential pumping is introduced in the SEM, via two apertures and an additional rotary pump. The PLAdiameter for ASEM was increased to 30µm. Scintillating BSE detectors are used. The concept of a portableelectron optics column to examine specimens at room conditions is introduced. Specimens were no more limitedby size, portability or nature: the idea is to take the microscope to the specimen and examine its natural surface.

203 Danilatos, G.D., Robinson, V.N.E., and Postale, R. (1980) An environmentalscanning electron microscope for studies of wet wool fibers. Proc. Sixth Quinquennial Wool TextileResearch Conference (26 Aug.-3 Sept., 1980), Pretoria, II:463-471.

key words: wool, applications

Abstract: An overview of ESEM with particular emphasis on its application to studies of wool fibers.

204 Danilatos, G.D. (1981a) The examination of fresh or living plant material in an environmentalscanning electron microscope. J. Microsc. 121:235-238.

key words: applications, plant material, botanical structures, live specimens

Abstract: An environmental scanning electron microscope (ESEM) has been developed which allows theexaminations of live and wet plant specimens. The results are compared with those obtained using similarmaterial that has been hydrated or prepared by conventional techniques. The plant materials can survive thehypobaric pressure and beam irradiation, especially if the latter is controlled.

205 Danilatos, G.D. (1981b) Design and construction of an atmospheric or environmental SEM (part 1).Scanning 4:9-20.

key words: high pressure, differential pumping, pressure characteristics, PLA, leak rate, apertureconductance, objective aperture, room temperature, wool, BSE, multiple-backscattered electrons (MBSE), design &construction of ESEM & ASEM, field of view, ASEM

Abstract: This is the first in a series of reports on the design and construction of an atmospheric orenvironmental SEM. The introduction of better vacuum pumping between the objective and pressure limitingaperture (PLA) has allowed the use of relatively large pressure limiting apertures, i.e., up to 57µm for operation atatmospheric pressure or up to 400µm for operation at saturation water vapor pressure and at one atmosphere, atroom temperature are presented. The first part of experimentation and analysis on the vacuum characteristics of



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the new system together with different detection configuration is also presented. An integrated detector/PLAsystem is proposed. By a multiple-backscattered electron (MBSE) imaging mode it is shown that the surface of aspecimen can be imaged although the BSE detector is placed below an (opaque) specimen.

206 Danilatos, G.D., Loo, S.K., Yeo, B.C. and McDonald, A. (1981) Environmental and atmosphericscanning electron microscopy of biological tissues. 19th Annual Conference of Anatomical Society ofAustralia and New Zealand, Hobart, J. Anatomy 133:465.

key words: biological ESEM, tissues, fresh materials, live specimens, applications

Abstract: Fresh, fixed and critical point dried specimens of rat trachea, stomach and skin were examinedwith the ESEM. Results showed that in tissues with fine surface detail such as trachea and stomach there wassome loss of contrast and resolution in the image when they were viewed in the fresh state. In a “harder” tissuesuch as skin, quite clear images could be obtained. A comparison of fresh and critical point dried skin showedsome distortion in the form of increased desquamation, and shrinkage in the critical point dried tissue. At present,the advantages of this technique seem to lie in the fact that some features of biological tissues which may bemasked by processing could be revealed. Living tissue can be examined. It is time saving as tissues do not need tobe fixed, dehydrated and critical point dried.

207 Danilatos, G.D., and Postale, R. (1982a) Advances in environmental and atmospheric scanningelectron microscopy. Proc. Seventh Australian Conf. El. Microsc. and Cell Biology, Micron 13:253-254.

key words: low keV, TV scan rate, gas dynamics, PLA tilt, wedge-shape BSE detector, multiple-backscattered electrons (MBSE), ASEM, live plant in atmosphere, live specimens

Abstract: Advances in ASEM and ESEM are presented. The PLA is tilted to avoid the effects of a gas jetforming above PLA. A wedge shaped BSE detector is used. The multiple-backscattered electrons contribute to theimage. Low (7) keV at TV scan rate is used to image salt crystal formation. Wool and live plant specimen isimaged at one atmosphere with 15keV. The PLA size of ASEM has been dramatically increased to 140µm foroperation at one atmospheric pressure

208 Danilatos, G.D., and Postale, R. (1982b) The environmental scanning electron microscope and itsapplications. Scanning Electron Microscopy 1982:1-16.

key words: low keV, TV scan rate, gas dynamics, PLA tilt, wedge-shape BSE detector, multiple-backscattered electrons (MBSE), ASEM, live plant in atmosphere, live specimens, rat tissue, live ants, fielddistortion, bright halo, critical review, Leptospermum flavescens, BSE detector (thin), BSE detector (wedge), wool,radiation effects, applications, review, outline

Abstract: A critical review of ESEM and its applications to date is presented. Wool fibers subjected tovarious treatments, wet (fresh) rat tissues, crystallization and rewetting o salts, and some radiation effects havebeen examined. A wedge shaped BSE detector together with a tilted aperture allowed the use of relatively low(7 keV) at TV scan rate.

209 Danilatos, G.D., and Postale, R. (1982c) The examination of wet and living specimens in a scanningelectron microscope. Proc. Xth Int. Congr. El. Microsc., Hamburg, 2:561-562.

key words: review (brief), review, outline

Abstract: Brief review of ESEM is presented.

210 Danilatos, G.D. (1983a) Gaseous detector device for an environmental electron probe microanalyzer.Research Disclosure No. 23311:284.

key words: gaseous detector device



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Abstract: First disclosure of gaseous detector device (GDD). This is a novel method in electron microscopywhereby the gaseous ionization produced by the signal-gas interactions is used for imaging.

211 Danilatos. G.D. (1983b) A gaseous detector device for an environmental SEM. Micron andMicroscopica Acta 14:307-319.

key words: gaseous detector device, ionization. SE detection with GDD. BSE detection with GDD, GDD-low bias, GDD

Abstract: This is the first paper announcing the gaseous detector device, by which the ionization producedin the gas by the signal-gas interactions is used for imaging. Ionizing radiation’s such as BSE and SE electronsproduce positive ions and free electrons in the gas. These charge carriers can be collected by electrodes placed invarious positions in the specimen chamber. The contrast varies with gas pressure, electrode positioning andelectrode or specimen bias level and polarity. The variation of ionization current measured with a Faraday cup andwith a ring electrode was measured. An inversion of contrast and corresponds to a “cross over” point of theionization current collected by the Faraday cup as we raise the pressure. Various contrast phenomena are recorded.

212 Danilatos, G.D., and Postale, R. (1983) Design and construction of an atmospheric or environmentalSEM-2. Micron 14:41-52.

key words: gas dynamics, jet, jet deflectors, jet length, high pressure, differential pumping, pressurecharacteristics, PLA, leak rate, objective aperture, room temperature, BSE, design & construction of ESEM &ASEM, field of view, ASEM

Abstract: This is a continuation of reports on the design and construction of an ESEM and ASEM. Itpresents a thorough experimental investigation of the gas dynamics in the system. Experiments specifically aimedto establish how the vacuum in the electron optics system was affected by the relative positioning of the objectiveand pressure limiting aperture, as well as the pumping speeds employed, specimen chamber pressure, geometryand size of apertures, and by other means. Further, the influence of the jet deflectors, to control the effects of thisjet on the microscope system were studied quantitatively using specifically designed apparatus. In addition, thestudy of the pressure gradients below the pressure limiting aperture revealed that specimens can be placed as closeas one radius from the aperture and still experience an almost saturated vapor pressure environment. The resultsof the present study are currently being used in the design of an optimum detection configuration. A preliminaryresult has allowed the use of 140 µm pressure limiting aperture to observe specimens at atmospheric pressures aswell as the use of accelerating voltages (e.g. 7 kV) at TV scanning rates to record video cassette dynamicphenomena, including wetting or recrystallizing salt solutions, etc.

213 Danilatos, G.D. (1984) The gas as a detection medium in the environmental SEM. Eighth AustralianConference on Electron Microscopy, Brisbane, Australian Academy of Science, Abstracts:9.

Abstract: Short review of gaseous detection

214 Danilatos, G.D., and Brancik, J.V. (1984) A microinjector system in the environmental SEM. EighthAustralian Conference on Electron Microscopy, Brisbane, Australian Academy of Science, Abstracts:34.

key words: microinjector, liquid flow, applications

Abstract: Some applications of ESEM required the invention of a device for the injection of micro dropletsof liquid onto the specimen in situ. The practical problem of transferring liquid from ambient pressure into thehypobaric environment has been solved by the following system: A small cavity behind a capillary needle in thespecimen chamber is filled or emptied with a liquid by means of two tubes leading outside the microscope. Theinternal diameter of the needle (20 µm) was chosen so as to conduct sufficient liquid when externally applied underpressure, whilst at other times allowing a negligible air leak. The needle can be moved in three dimensions withcontrols independent from the microscope stage. To accommodate the moving needle and specimen within 1 mm



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from the pressure limiting aperture a BSE detector integrated with PLA was constructed. This arrangement hasbeen used to obtain video recordings of various systems.

215 Danilatos, G.D., Denby, E.F., and Algie, J.E. (1984) The effect of relative humidity on the shape ofBacillus apiarius spores. Current Microbiology 10:313-316.

key words; Bacillus apiarius, biological ESEM, spores, applications

Abstract: Bacillus apiarius spores have been examined at relative humidities between 99% and 12% in anESEM. The spores have also been studied both wet and dry with an interference microscope. Their shape remainsrectangular whether wet or dry. A calculation of the effect of an osmotic pressure change of about 200 atm uponthe maximum deflection of the longest side of the spire shows that the deflection is less than 4.5 nm. The shape ofthe spore therefore is not markedly affected by a change from dry to wet and the shape will remain as it was whenthe coat was initially formed, unless the coat is weakened by some chemical attack. The refractive index of the coatmaterial is 1.532-1.536.

216 Danilatos, G.D. (1985) Design and construction of an atmospheric or environmental SEM (part 3).Scanning 7:26-42.

key words: high pressure, differential pumping, pressure characteristics, PLA, leak rate, apertureconductance, BSE, design & construction of ESEM & ASEM, ASEM, double BSE, detector, light pipe, lighttransmittance, optimum BSE, collection angle, atomic number, contrast, Z-contrast, topography, optimumclearance

Abstract: The continuation of the advances in the design and construction of ESEM and ASEM is reported.A pair of scintillator backscattered electron detectors have been designed and made so that signal processing toenhance topography and Z-contrast can be performed. Optimum shapes and positioning of the detectors have beendetermined. The light transmittance in the light pipe has been mapped and measured to be 51%. Satisfactorysignal-to-noise-ratio images of a carbon specimen have been obtained with 5 kV, 2 pA and 50 s scan time at 0.1mbar. With a higher intensity beam, clear images of wool fibers have been achieved at one atmosphere. TheASEM and ESEM have been shown to operate both under conditions of a gaseous environment and with detectionmodes used in other microscopes. Changes and phenomena occurring as the relative humidity varies between 0and 100% have been recorded. With ASEM, imaging was possible with a 150µm PLA at 10 keV.

217 Danilatos, G.D., and Brooks, J.B. (1985) Environmental SEM in wool research present state of theart. Proc. 7th Int. Wool Textile Research Conference, Tokyo, I:263-272.

key words: applications, wool, greasy wool, wetting studies, scouring of wool, chemical treatments. fiberextension, radiation effects, contact angle, review, outline

Abstract: The new technique of ESEM has been developed to a highly efficient operational state. It hasbeen used to study greasy wool fibers treated and untreated, wet and dry, to study mechanical properties in situ andto observe liquid spreading on the fiber surface. An examination of the effect of the electron beam has beenundertaken under various irradiation and environmental conditions.

218 Danilatos, G.D. (1986a) Environmental and atmospheric SEM - an update. Ninth AustralianConference on Electron Microscopy, Australian Academy of Science, Sydney, Abstracts:25.

Abstract: Short review

219 Danilatos, G.D. (1986b) Color micrographs for backscattered electron signals in the SEM. Scanning8:9-18.

key words: color imaging, BSE in color



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Abstract: The backscattered electron (BSE) signals detected by a pair of detectors in the ESEM can be usedfor producing color micrographs. The image corresponding to any of these signals, or to a mixture of thesesignals, is assigned one primary color, and two or more of these images are superimposed onto the same colorframe. In addition, the mixing of-signals from the gaseous detector device together with their use for colorimaging is also examined.

221 Danilatos, G.D. (1986d) Improvements an the gaseous detector device. Proc. 44 Annual MeetingEMSA:630-631.

key words: gaseous detection device, GDD, multi-electrode GDD

Abstract: Two wires are used for the gaseous detection device (GDD). Directionality contrast is produced.By adding the outputs from GDD, atomic number contrast is produced equivalent to that obtained with a pair ofscintillating BSE detectors. By subtracting the outputs, topography contrast is produced. By inverting theelectrode bias, the contrast is inverted.

222 Danilatos, G.D. (1986e) ESEM - A multipurpose surface electron microscope. Proc. 44th AnnualMeeting EMSA:632-633.

key words: terminology, acronyms ESEM and ASEM, solid state detectors

Abstract: Brief review of ESEM. Proposal to unify the terms of ASEM and ESEM to one only, namely,ESEM. Design of integrated solid state detectors for the general ESEM.

223 Danilatos, G.D. (1986f) Beam-radiation effects on wool in the ESEM. Proc. 44th Annual MeetingEMSA:674-675.

key words: radiation effects, wool

Abstract: Various beam irradiation effects on wool fibers are reported. The type and amount of beameffects depend on (a) the electron beam: accelerating voltage, current intensity, scanning mode (raster or other, linedensity, magnification), (b) the environment: nature, pressure and temperature of gas and (c) the specimen:composition, structure, texture and orientation.

224 Danilatos, G.D. (1986g) Specifications of a prototype environmental SEM. Proc. XIth Congress onElectron Microscopy, Kyoto, I:377-378.

key words: specifications of ESEM, commercial ESEM, integration, universal ESEM

Abstract: A summary of ESEM specifications is presented with a view to designing a commercial ESEM.The concept of integrating various fundamental components is introduced: For a commercial instrument weshould integrate (a) objective lens and scanning coils with (b) differential pumping and with (c) detection systems,all in a new design. The concept of a universal ESEM is introduced, whereby ESEM can perform both as aconventional SEM and as an ESEM.

225 Danilatos, G.D. (1986h) Cathodoluminescence and gaseous scintillation in the environmental SEM.Scanning 8:279-284.

key words: cathodoluminescence, gaseous scintillation, gaseous detection device, GDD, generalized GDD

Abstract: A novel detection means for the environmental SEM (ESEM) is described. Certain gases, apartfrom being the environmental conditioning medium, can also act as a scintillator detector. All signals, such assecondary and backscattered electrons which can cause a particular gas to luminescence, can be detected. It isfurther concluded that the gas can act as a generalized detector device for all signal-gas reactions provided somesuitable parameter can be monitored. New possibilities in the detection of specimen cathodoluminescence createdby the ESEM are demonstrated.



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226 Danilatos, G.D., and Brancik, J.V. (1986) Observation of Liquid transport in the ESEM. Proc. 44thAnnual Meeting EMSA:678-679.

key words: microinjector, liquid flow, applications

Abstract: The microinjector previously developed and reported has been used in various applications. It ispossible to form a droplet standing at the tip of the needle of the microinjector and move around the object underexamination to make contact with the liquid. The subsequent wetting, absorption or reaction of the liquid can beviewed at TV scanning rates and a video recording can be made for further analysis. With this system it has beenpossible-to observe the wetting and removal of different components from the surface of greasy (raw) wool fibers.Apart from the specific wool applications, other industrial and scientific investigations can benefit. Videorecordings of various liquids and liquid transport is shown. The flow and absorption of water by paper tissue atvarious “instants” is captured. The fast changes of configuration of liquids can be captured in real time forsubsequent study. The ESEM equipped with this system has created new possibilities for surface physics andchemistry.

227 Danilatos, G.D. (1988a) Foundations of Environmental Scanning Electron Microscopy. Advances inElectronics and Electron Physics, Academic Press, Vol. 71:109-250.

key words: high pressure, differential pumping, pressure characteristics, PLA, leak rate, apertureconductance, BSE, gas dynamics, jet, definition of ESEM, terminology, gas flow, gas equations, beam-gasinteractions, beam-specimen interactions, specimen-signal interactions, signal-gas interactions, gas-specimeninteractions, beam-signal interactions, scattering cross-sections, beam profiles, electron skirt, skirt, electrondistribution, beam diameter, interaction volume in gas, gaseous reactions, ionization, scintillation, gas scintillation,ion concentration, electrostatic Pinch effect, secondary electrons, cathodoluminescence, x-rays, Auger electrons,gaseous detection device, resolving power, signal-to-noise-ratio, SNR, radiation effects, charging, contamination,damage, ESEM operation, application, oligo-scattering, plural scattering, single scattering, multiple scattering,molecular flow, continuum flow (viscous effusion), mean free path, beam spread, reduced variables, Gaussiandistribution, Faraday cup, spot width, beam transfer, salts, contrast, resolution, live specimens, wool, probe,electron probe. distribution, skirt radius, cross-section, elastic cross-section, scattering

Abstract: A comprehensive survey on the fundamentals of ESEM is presented. A formal definition ofESEM is proposed. The state of gas in ESEM is given, namely, the basic equations frequently needed, an analysisof the gas flow, calculation of conductance and experimental assessment of gas flow. The general interactions inESEM are outlined by way of pointing to all possible combinations of dual component systems. Above all, themain thrust of this survey concentrates around the fundamental question of electron beam scattering anddistribution in gas. Until this time, there have been conflicting reports on whether the useful beam spot spreads ornot. Applying complex mathematical formulas that describe the electron scattering and distribution in a pluralscattering regime, a definitive answer was found for the first time: Fraction of electrons is removed from theoriginal beam in vacuum and is redistributed in a very broad “skirt” surrounding the remaining intact fraction atthe center. This result is further confirmed by careful experimentation.

This finding is extremely significant, because it means that the resolving power of ESEM can be maintained in thepresence of gas. The preservation of a core electron beam with the same distribution as in vacuum occurs over afinite beam travel distance at a given gas pressure. This regime is characterized by the condition that the averagenumber of collisions per electron is less than three, and it has been termed "oligo-scattering" regime. In the courseof this study, calculations of scattering cross-sections for atomic and molecular gases and profiles of skirts for a"point" beam and for a Gaussian distribution beam have been found. Furthermore, the beam-gas interactionvolume, ionization of gases, ion concentration, and electrostatic effects are analyzed. All detection modes, namely,BSE, SE, CL, x-ray and Auger electrons are discussed in detail. The multipurpose gaseous detection device isreviewed. Analytical equations of signal-to-noise-ratio and a thorough examination of contras and resolution isundertaken. The beam radiation effects, namely, charging, contamination and damage are discussed. Some basicconsiderations for the operation and application of ESEM are outlined. This survey is an up-date of the state of theart in ESEM at present.



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228 Danilatos, G.D. (1988b) Electron beam profile in the ESEM. Proc. 46th Annual Meeting EMSA:192-193.

key words: resolution, profile, electron distribution, skirt, scattering

Abstract: This is a summary on the electron beam profiles and resolution based on a previous extendedsurvey.

229 Danilatos, G.D. (1988c) Contrast and resolution in the ESEM. Proc. 46th Annual Meeting EMSA:222-223.

key words: contrast, resolution, signal-to-noise-ratio

Abstract: This is a summary on contrast and resolution based on a previous survey.

230 Danilatos, G.D. (1989a) Surface chemistry in the ESEM. Pittsburgh Conference and Exposition(Atlanta) 1989, Abstracts, paper No. 360.

key words: chemistry in ESEM, surface chemistry

Abstract: A brief review of ESEM with emphasis on chemistry in the system.

231 Danilatos, G.D. (1989b) Environmental SEM: a new instrument, a new dimension. Proc. EMAG-MICRO 89, Inst. Phys. Conf. Ser. No 98, Vol. 1:455-458. (also Abstract in: Proc. Roy. Microsc. Soc. Vol.24, Part 4, p. S93).

key words: resolution micrograph, integration ESD/BSE, ElectroScan ESEM. review, outline

Abstract: A concise review of ESEM with early micrographs from the ElectroScan ESEM. Efficientscintillator design in conjunction with a sharp tip ESD. The fundamental aspects of ESEM are outlined in the fourpage extended abstract.

232 Richard Harneman ESEM Uses Vacuum Gradients to Examine Wet and Uncoated NonconductiveSamples, Research & Development September 1988 © 1988 Cahners Publishing Company

Key Words:

Abstract: Environmental Scanning Electron Microscope (ESEM) eliminates sample preparation and allowsmaterials to be examined in their natural states.

233 Danilatos, G.D. (1990a) Design and construction of an environmental SEM (part 4). Scanning 12:23-27. (originally submitted , Nov. 1987)

key words: integration, PLA-detector, GDD, high pressure, design & construction of ESEM & ASEM,ASEM, GDD above PLA

Abstract: A new detection configuration using the gaseous device in the environmental scanning electronmicroscope (ESEM) is demonstrated. First, the pressure-limiting aperture (PLA) is used simultaneously as abiased electrode to collect the ionization current produced in the gaseous environment of the microscope. Second,a wire electrode is placed above the pressure-limiting aperture, and it is shown that enough signal from thespecimen escapes through the aperture to produced satisfactory images. These detection configurations allow theuse of high specimen chamber pressures, namely, well above 200 mbar. Above this pressure level, life is fullysustainable. This report presents one example of unify the detection of signals both below and above the PLA1 byuse of the gaseous detector device. This unification further confirms the need for unifying also the terms ASEMand ESEM into one, namely, ESEM, as proposed earlier.

234 Danilatos, G.D. (1990b) Fundamentals of environmental SEM. Eleventh Australian Conf. El. Microsc.,University of Melbourne, Abstracts.



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Abstract: Review abstract.

235 Danilatos, G.D. (1990c) Theory of the Gaseous Detector Device in the ESEM. Advances inElectronics and Electron Physics, Academic Press, Vol. 78:1-102.

key words:- GDD, theory of GDD, imaging parameters; induction, displacement current electrontemperature, ion temperature, electron mobility, ion mobility, mobility, diffusion, electron diffusion,recombination, electron attachment, ionization, ionization energy, terminology, terms, discharge, amplification,gain, Townsend coefficient, Townsend factors, drift velocity, plane electrodes, parallel plates, Paschen law,primary processes, secondary processes, time response, frequency response, scintillation GDD, spectroscopy,statistics, energy resolution, Geiger-Muller,- counters, proportional counters, detection volume, amplificationvolume, electrode geometry, multi-electrode GDD, cylindrical geometry, avalanche, fast electrons, slow electrons,probe, object, gas, walls, electrons, ions, rays, slow, fast, light, specimen current, absorbed current

Abstract: A comprehensive theoretical survey and analysis of the gaseous detector device is presented. It isestablished that the true and correct nature of signal generated on various electrodes is induction. As long as thereare moving charges in the inter-electrode space, a signal current flows in the external circuit. The theory ofinduced signals in general and in the ESEM, in particular, is given. It is shown that the conventional notion of"specimen absorbed current" is misleading and can lead to erroneous results in ESEM. An image can be madeeven if no "absorbed" current by the specimen is present. The electrical conductivity of a specimen is responsiblefor the after-effects of charging and image distortion in the vacuum SEM. The magnitudes of imaging parametersin ESEM are calculated, and a realistic picture is conveyed. This survey includes a detailed collection and analysisof various physical parameters such as electron and ion temperature, electron and ion mobilities, electron diffusion,recombination, electron attachment and effective ionization energy. To describe the new complex physicalphenomena in electron microscopy, a new terminology is necessitated and proposed. The discharge characteristicswith regard to electrode geometry, nature of gas, and electrode bias are explained. The amplification or gaincharacteristics of the GDD are thoroughly analyzed for various electrode geometry’s. The limits and advantagesare determined. Apart from the ionization GDD, the scintillation GDD is shown to have some unique advantagesin performance. Considering the spectroscopy, statistics and energy resolution it is proposed that nuclear methodsand instruments can be transferred and properly adapted to electron microscopy in general and, in particular, toenvironmental scanning transmission electron microscopy and to ESEM. Practical tips and construction detailsare gathered for efficient designs of GDD.

236 Klaus-Ruediger Peters, Surface Imaging of the Natural Air Interface of Hydrated Lung Tissue,Molecular Imaging Laboratory, Dept. of Radiology Biomolecular Structure Analysis Center, University ofConnecticut Health Center, Farmington, CT

237 Klaus-Ruediger Peters, Introduction to the Technique of Environmental Scanning ElectronMicroscopy, Molecular Imaging Laboratory, Dept. of Radiology Biomolecular Structure Analysis Center,University of Connecticut Health Center, Farmington, CT

238 Danilatos, G.D. (1990f) Detection by induction in the environmental SEM. Electron Microscopy 1990,Proc. XIIth Int. Confer. El. Microsc. (Ed. Peachey and Williams), San Francisco Press, Vol. 1:372-373.

key words: induction, specimen current, absorbed current

Abstract: Further demonstration and review of the mechanism of detection by indication is presented. Saltcrystals resting on a glass plate were imaged both by a flat electrode above the specimen and a flat electrode belowthe glass plate. The images were equivalent (the same) after inverting one of them. This proves that theconventional concept of "absorbed' specimen current, is both redundant and non-existent. Instead, detection byinduction is the ever present mechanism for all specimens, conducting and insulating.



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239 Danilatos, G.D. (1991a) Review and outline of environmental SEM at present. J. Microsc. 162:391-402.

key words: review, ElectroScan, outline

Abstract: An up-date of ESEM is presented. Applications and imaging by use of the ElectroScan ESEMare included.

240 Danilatos, G.D. (1991b) Gas flow properties in the environmental SEM. Microbeam Analysis-1991(Ed. D G Howitt), San Francisco Press, San Francisco:201-203.

key words: flow field, flow properties, temperature, speed, density, pressure, PLA, gas jet, pressure gradients,Monte Carlo, gas dynamics

Abstract: The flow properties, namely, gas density, temperature and speed are presented for the case of aflat pressure limiting aperture (PLA). It is important to know the variation of these properties in the immediateneighborhood of the PLA, through which the electron beam passes and near which the specimen must be placed.The direct simulation Monte Carlo method was used. The gas jet forming through an aperture was actuallyimaged with gaseous detection device.

241 Danilatos, G.D. (1992b) Gas flow in the ESEM Proc. ACEM-12 & ANZSCB-11 Univ. of WesternAustralia, Perth:57.

Abstract: Short review of flow field properties.

242 Danilatos, G.D. (1992b) Gas flow in the environmental SEM. Proc. 50th Annual Meeting EMSA (EdG.W. Bailey, J Bentley and JA Small), San Francisco Press, San Francisco:1298-1299.

key words: flow field, flow properties, pressure PLA, gas jet, Monte Carlo, gas dynamics, sharp PLA

Abstract: Further results from a study on gas dynamics in ESEM are presented. The flow field around aconical-sharp pressure limiting aperture is analyzed by the direct simulation Monte Carlo method. The variationof flow field properties with different specimen clearances is presented. One conclusion is that the specimensurface pressure is practically unaffected by the gas flow when the specimen is placed further away than one PLAdiameter. The calculation of gas density gradients along the axis of the system is needed for the determination ofmass density and electron scattering.

243 Danilatos, G.D. (1992c) Secondary-electron imaging by scintillating gaseous detection device. Proc.50th Annual Meeting EMSA (Ed G.W. Bailey, J Bentley and JA Small), San Francisco Press, SanFrancisco:1302-1303.

key words: scintillation, GDD, gaseous scintillation, secondary electrons, SE, control specimen

Abstract: An alternative way to detect secondary electrons in a gaseous environment is by use of thegaseous scintillation that accompanies an electron avalanche. Generally, apart fro ionization we also have electronexcitation as the electrons collide with gas molecules in the multiplication process. The gaseous scintillation canbe detected with a suitable light pipe/PMT (photomultipler) system. Results showing definite SE image arepresented. It was found that the SE images could also be obtained at TV scanning rates, which shows that theGDD frequency response is very broad. This is consistent with short electron transit times previously calculated.

244 Danilatos, G.D. (1993a) Environmental scanning electron microscope-some critical issues.

key words: universal ESEM, flow field, flow properties, pressure PLA, gas jet, pressure gradients, MonteCarlo, gas dynamics, sharp PLA, beam transfer, transition region, electron diffusion, mass thickness, noisepropagation, solid scintillating BSED, charge neutralization, low vacuum SEM, low voltage SEM, signal-to-noise-



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ration, SNR, detector efficiency, E-T detector, SE detector, surface charge accumulation, critique, review, criticalissues, grids, YAG, YAP, cathodoluminescence, CL, x-rays, multi-electrode GDD

Abstract This is both a review and a survey into some critical issues of the environmental scanning electronmicroscope (ESEM). Some new concepts and designs are also presented. An attempt to unify various detectionmodes is made. In ESEM, the gas flow around the main pressure limiting aperture establishes a density gradientthrough which the electron beam passes. Electron beam losses occur in this transition region and in the uniformgas layer above the specimen surface. In the oligo-scattering regime, the electron distribution consists of a widelyscattered fraction of electrons surrounding an intact focused probe. The secondary electrons are multiplied bymeans of gaseous ionization and detected both by the ionization current and the accompanying gaseousscintillation. The distribution of secondary electrons is governed by the applied external electric and magneticfields and by electron diffusion in the gas. The backscattered electrons are detected both by means of the gaseousdetection device and by solid scintillating detectors. Uncoated solid detectors offer the lowest signal to noise rationespecially under low beam accelerating voltages. The lowest pressure of operation with uncoated detectors hasbeen expanded by the deliberate introduction of a gaseous discharge near the detector. The gaseous scintillationalso offers the possibility of low noise detection and signal discrimination. The “absorbed” specimen current”mode is re-examined in the conditions of ESEM and it is found that the current flowing through the specimen isnot the contrast forming mechanism: I is all the electric carriers in motion that induce signals on the surroundingelectrodes. The electric conductivity of the specimen may affect the contrast only indirectly, i.e., as a secondary,not a primary process. The ESEM can operate under any environment including high and low pressure, low orrough vacuum and high vacuum; it also operates at both high and low beam accelerating voltage, so that it may beconsidered as the universal instrument for virtually any application previously accessible or not to the conventionalSEM.

245 Danilatos, G.D. (1993b) Environmental scanning electron microscopy and microanalysis.Mikrochimia Acta, submitted.

key words: review, universal ESEM, operational range, parameters, ablation, spectrometry, massspectrometer, x-rays, skirt, transition, Mach disk, SE, BSE, Cl

Abstract: This is a review of ESEM whereby the main principles and instrument design considerations areunified in order to define the range of various operational parameter as we vary pressure. It is shown that theenvironmental scanning electron microscope is the natural extension of the scanning electron microscope. Theformer incorporates all of the conventional functions of the latter and, in addition, it opens many new ways oflooking at virtually any specimen, wet or dry, insulating or conducting. he environmental scanning electronmicroscope is characterized by the possibility of maintaining a gaseous pressure in the specimen chamber. Alloperational parameters can be varied within a range which is a function of pressure. It can be used with all typesof gun and basic modes of detection and, hence, it can be applied to both morphological and to microanalyticalstudies. It has opened many novel ways of looking at specimens and phenomena not previous accessible withscanning electron microscopy. A model for specimen charge distribution and dissipation is proposed. Theinterface of a mass spectro meter by sampling the gas flowing through the PLA is suggested; this would give rise tohigh resolution ablation mass spectrometry. An outline of present approaches to the problem of electron skirt inmicroanalysis is presented.

246 Danilatos, G.D. (1993c) Environmental scanning electron microscope: A new tool for inspection andtesting. Jap. J. Appl. Phys. (submitted).

key words: field emission, wafers, electronic devices, line width measurement, inspection, testing, low keV,Nikon Corporation, Critical Measurement, applications

Abstract: This is a review with particular emphasis on the application of ESEM technology to theexamination of electronic devices. Because of its universal capabilities, ESEM is ideally suited for inspection andtesting, in general. In particular, microelectronic devices can now be studied faster, better and more reliably, oreven in ways not previously feasible. For wafer pattern measurements, the high resolutions required need not becompromised by the use of a very low keV incident beam. It is much better to use rather a compromise voltage of,



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say, 3 keV to avoid specimen damage and yet to allow a high resolution. At the same time, specimen charging isavoided by maintaining a gaseous pressure around 100-200 Pa. A dedicated instrument with a field emission gunhas been developed for linewidth measurements (Critical Dimension Measuring SEM, Nikon Corporation). Apartfrom inspection and testing, ESEM has potential for a wide range of applications in microprocess industry andresearch, because the natural surface of a specimen can be placed directly under the beam. There seems only theneed to control the amount and nature of gas for each particular application. In fact, the very presence of acontrolled gaseous environment has opened up many new possibilities for beam-specimen and gas-specimeninteractions. Electron beam-induced chemical reactions and applications to direct writing and associated processescan be given a new impetus. Resist materials and processing techniques can also be studied in a new way. Bothetching and carbonaceous depositions have been observed and it is envisaged that these processes can be used in acontrolled way during imaging to monitor those processes and to put them to practical use. Electron lithographyand micro fabrication are yet to see the benefits of ESEM. Hot and cold stages can be incorporated in themicroscope for studies of materials in situ at high, intermediate and low temperatures. Already, several studies onsoldering techniques with this technology have appeared in the literature, and transition phases of materials fromvery low to very high temperatures can be readily monitored. The range of ESEM uses can only be underestimatedat this early stage of development.

247 Danilatos, G.D. (1993d) Universal ESEM. Proc. 51st Annual Meeting EMSA, submitted.

key words: universal ESEM, mass spectrometer, multiple-detectors

Abstract: A universal system of detectors can now be incorporated in ESEM so that the complete pressurerange from high pressure to high vacuum can be used. The GDD is integrated with solid scintillating materialstogether with an optimized gas dynamics system. An array of electrodes (grids and apertures) serve in thedetection, separation and control of various signals. They are combined with highly efficient scintillating materialsand/or light pipes. This system should be incorporated at the lower part of an electron optics column. Thus, allmain modes of detection can be represented. Secondary (SE) and backscattered (BSE) electron signals,cathodoluminescence (CL) and x-ray microanalysis can be practiced at any pressure. In addition, a massspectrometer can be interfaced for analysis of the gas flowing through PLA1. By directing the electron beam at thefeature of interest, ESEM produces an ablation mass spectrometer with very high resolution and sensitivity, in anequivalent but much better system than that used with a laser beam.

248 Danilatos, G.D. (1993e) An introduction to ESEM instrument. Microsc. Res. Technique, in press

key words: ElectroScan ESE, electron optics column, differential pumping, pumping manifold, ESD,ElectroScan BSED, working distance, clearance, bullet, pressure stages, BSE collection angle, light pipe

Abstract: An outline is presented of the first commercial environmental scanning electron microscope(ESEM) made by ElectroScan Corporation. A concise description of this instrument and its operation, from auser’s perspective, is given. More specifically, the description includes the electron optics, pressure stages andcontrol, detection modes, resolution and ancillary equipment.

249 Danilatos, G.D. (1993f) Biography of environmental scanning electron microscopy. Microsc. Res. andTechnique, in press

key words: survey of ESEM, review of ESEM, development of ESEM, applications, ElectroScan,ElectroScan ESEM

Abstract: Two comprehensive and updated lists of publications on environmental scanning electronmicroscopy are compiled. One list contains mainly those papers dealing with the development andinstrumentation, while the other deals with the applications of the technique. A brief introductory summary of thefield is presented.

250 C.E. Jordan and A.R Marder, A Model For Galvanneal Morphology Development The PhysicalMetallurgy of Zinc Coated Steel.



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Abstract: Cross-sectional and planar views of galvanneal coatings were studied to characterize morphologydevelopment. Cross-sectional analysis of coatings annealed under different time-temperature conditions showedthe formation of three distinct morphological coating types. The morphology types were classified as Type-0,Type-1, and Type-2 and represent an under alloyed, a marginally alloyed, and an over alloyed coating structure,respectively. The structures were analyzed to quantify the chemistry associated with each morphology. Planarobservation of the coatings during annealing was performed in-situ in an environmental SEM. Burst-likestructures were found to form during annealing, and the role of bath aluminum content on their formation wasstudied. From these results a phenomenological model for galvanneal morphology development is proposed.

251 Weiying Tao and Billie J. Collier. The Environmental Scanning Electron Microscope: A new Tool forTextile Studies

Key Words: Analytical Techniques, Environmental Scanning Electron Microscope (ESEM), FiberMorphology, Fiber Structure, Microscopy, Nondestructive Testing, Surface Examination

Abstract: Use of the environmental scanning electron microscope (ESEM) for surface examination andobservation of textile materials under varying conditions is explored. The ESEM allows imaging of specimenswithout coating and drying, as well as the observation of dynamic phenomena. Examples of textile structuresviewed with the ESEM are shown, including time series images of fabric absorption and structure change underwetting and heating. The advantages of ESEM over regular scanning electron microscopy (SEM) are alsodiscussed.

252 Y.Xi, T.B. Bergstrom and H.M. Jennings, Image intensity Matching Technique: Application to theEnvironmental Scanning Electron Microscope Computational Materials Science 2 (1994) 249-260

Abstract: An image analysis technique, called image intensity matching, is developed and is shown to besuitable for studying the complex sub-pixel deformation on ESEM images. The technique is general but is appliedhere to dimensional changes that occur as cement past shrinks. The technique is based on a minimum meansquare error criterion. The relationship between the present technique and the maximum cross correlation methodis analyzed mathematically, and the latter is shown to be a special case in the minimum mean square errorcriterion. Noise is removed by a normalization process. The optimal window size is analyzed. The deformationparameters (for the problem in two dimensions) of rigid body translation, expansion or shrinkage, shear, androtation in a deformed image can be determined. The resolution is calibrated using a simulated image shift and isshown to be about 0.2 pixel

253 P. Forsberg and P. Lepoutre, ESEM Examination of Paper In High Moisture Environment: SurfaceStructural Changes and Electron Beam Damage. Scanning Microscopy 8 (1)

Key words: Wood Fibers, paper, fiber-rising, electron microscopy, surface properties, contact angle,supercalendered paper (SC), and light-weight coated paper (LWC).

Abstract: Supercalendered and coated papers (SC and LWC) were examined using and environmentalscanning electron microscope (ESEM). Moderate structural surface changes were observed as water condensed onthe surface in a high moisture environment. The changes were fully or partially reversible depending on thesample origin. A wide range of contact angles could be observed when condensing water on uncoated wood fibers.While there was no visible indication or irradiation damage on the commercial paper samples examined nor onmechanical pulp fibers, attempts to look at chemical pulp fibers during wetting to examine fiber swelling wereunsuccessful because of very rapid irradiation damage.

254 P. Forsberg and P. Lepoutre, ESEM Examination of the roughening of paper in high moistureenvironment. Presented at the 1993 PTS Symposium in Munich, Germany

Key Words: Fibers, Paper, Fiber-rising, Electron microscopy, Surface properties, LWC, SC, Gloss

Abstract: Supercalendered filled (SC) and light weight coated (LWC) papers were examined using anenvironmental scanning electron microscope (ESEM). Large structural surface chances were observed during



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condensation of water on the surface in a high moisture environment. The changes were fully or partiallyreversible upon drying depending on the sample origin. In the case of LWC papers, underlying fibers protrude andappear extensively swollen. Careful examination of the base stock confirmed that all Kraft fibers were collapsedinto ribbons but, during wetting, there was no evidence of ribbon-to-tube shape change of individual fibers.Swelling, which could be very substantial since the WRV indicates a potential swelling of more than 100% tookplace from flat ribbon to swollen ribbon. Upon drying the swollen ribbons shrunk back to their originaldimensions. Once supercalendered, the LWC base stock did show evidence of some collapsed mechanical fibersegments returning, irreversibly, to their uncollapsed state. In the case of SC papers, significant surfaceroughening during wetting was clearly seen but there was no indication of ribbon-to-tube shape changes either.Roughness and gloss changes measured after wetting on a laboratory printing press agreed well with ESEMobservations

255 L. Mott, S.M. Shaler, L.H. Groom, The Tensile Testing of Individual Wood Fibers UsingEnvironmental Scanning Electron Microscopy and Video Image Analysis. Submitted to TAPPIJournal

Key Words: Environmental Scanning electron microscopy, individual fibers, mechanical properties, digitalimage correlation, recycling, tensile, fiber failure

Abstract: Relationships between virgin fiber types, fiber production techniques and mechanical propertiesare well understood and documented (e.g.1). For recycled fibers, however, these same relationships areconfounded by unquantified degrees of further mechanical and chemical damage (2). To gain a morecomprehensive understanding of the impact of recycling on secondary fibers, the potentially deleterious effect ofrecycling upon fiber mechanical properties must be quantified. In this study individual fibers, both recycled andvirgin were tested in tension within and environmental scanning electron microscope. Fiber failure characteristicsof both recycled and virgin fibers are reported. The influence of both natural and processing induced gross defectswere seen to be highly influential in controlling mechanical behavior. The importance of defects and theimplications for modeling the behavior of fibers is explained.

256 G.D. Danilatos, Introduction to the ESEM, Instrument Microscopy Research andVol. 25, #5&6

Key Words: Environmental SEM, Scanning electron microscope, Gaseous detection, Differential pumping

Abstract: An outline is presented of the first commercial environmental scanning electron microscope(ESEM). A concise description of this instrument and its operation, from a users perspective, is given. Morespecifically, the description includes the electron optics, pressure stages and control, detection modes, resolution,and ancillary equipment.

256 R.E. De La Para, A Method to Detect Variations in the Wetting Properties of Microporous PolymerMembranes. Microscopy Research and Technique 25:362-373 (1993)

Key Words: ESEM, Hydrophobic, Hydrophilic, Water Condensation, Water droplets

Abstract: With the ability to perform dynamic experiments in the environmental electron microscope(ESEM), the evaluation of microporous polymer membranes via a scanning electron microscope has advancedbeyond morphological and elemental analysis. By adjusting sample temperature and environmental chamberpressure, the process of condensing water onto the porous membrane surface can be achieved. In doing so,assessments about the uniformity of wetting in hydrophilic membranes can be obtained based on how the liquidwater spreads. Variations in the shape of condensed water droplets formed on non-water wetting structures willreflect the degree of hydrophobicity. This technique has proven useful in the characterization of hydrophobic spotson chemically modified hydrophilic structures and the dynamic examination of irregular wetting patterns innaturally hydrophilic membranes.



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257 P. Messier and M. Vitale, Cracking in Albumen Photographs: An ESEM Investigation. MicroscopyResearch and Technique 25:374-383

Key Words: Conservation, Water, Relative Humidity, Cracking

Abstract: The preservation of nineteenth-century albumen prints is of great concern to collection managersand to conservators of photographic materials. In the field of art conservation preservation techniquesincorporating aqueous treatments are often used to enhance the long-and short-term stability of historical artifactsor art objects. In a study of the interaction of water with albumen photographs, experiments were carried out in theESEM to follow the real time effects of water on the prints. The experiments were designed to observe the effectsof a range of relative humidities and liquid water on samples of expendable historic albumen prints, utilizing theadvantages of imaging in the presence of water vapor. All albumen photographs exhibit a fine network of cracksin the albumen protein layer. Average crack width is approximately 10 am. as observed in the ESEM, a 4.25-foldincrease in the width of a single crack (at 50% RH), viewed normal to the surface, resulted from a single controlledexcursion to high relative humidity and swelling and shrinkage in thickness, and a 5% and 9% swelling andshrinkage along the width of a fragment of the albumen/image layer when the sample was immersed in water anddried. The visual information gained through the use of the ESEM helped to focus a materials investigation andserved as a foundation for a study which shows that aqueous treatment causes increased cracking of bothunsupported albumen and the albumen/image layer in prints

258 J.H. Rask, J.E. Flood, J.K. Borchardt, and G.A. York The ESEM Used to Image Crystalline Structuresof Polymers and to Image Ink on Paper. Microscopy Research and Technique 25:384-392.

Key Words: Apherulite, Polymer etching, Deinking, Paper recycling

Abstract: This article describes two cases in which the advantages of the ESEM have been exploited inunanticipated ways. First, we have found that etching occurs as the electron beam scans the surface of uncoatedpolymers in the ESEM. The surface topography caused by etching, as seen in the ESEM images, reflects themorphology of crystalline structures in the polymers. This technique has been valuable in the study of suchtextures in polymers. The second applications is related to our use of the ESEM in support of research on thedeinking of paper. In this effort we have learned that unconventional contrast mechanism can be used duringESEM imaging to distinguish between inked and non-inked areas of newsprint. Under usual operating conditions,ESEM imaging does not distinguish between inked and non-inked areas. However, at relatively low samplechamber pressures the non-inked areas appear brighter than inked areas in ESEM images.

259 S.P. Collins, R.K. Pope, R.W. Scheetz, R.I Ray, P.A. Wagner, B.J. Little Advantages of EnvironmentalScanning Electron Microscopy in Studies of Micro organisms. Microscopy Research and Technique25:398-405

Key Word: Environmental Scanning Electron Microscopy, Algae, Fungi

Abstract: Microorganisms, including bacteria, fungi, protozoa, and micro algae, are composed,predominantly of water which prohibits direct observation in a traditional scanning electron microscope (SEM).Preparation for SEM requires that microorganisms be fixed, frozen or dehydrated, and coated with a conductivefilm before observation in a high vacuum environment. Sample preparation may mechanically disturb delicatesamples, compromise morphological information, and introduce other artifacts. The environmental scanningelectron microscope (ESEM) provides a technology for imaging hydrated or dehydrated biological samples withminimal manipulation and without the need for conductive coatings

Sporulating cultures of three fungi, a Spergillus sp., Cunninghamella sp., and Mucor sp., were imaged inthe ESEM to assess usefulness of the instrument in the direct observation of delicate, uncoated, biologicalspecimens. Asexual sporophores showed no evidence of conical displacement or disruption of sporangia.

Uncoated algae cells of Euglena gracilis and Spirogyra sp. were examined using the backscatter electrondetector (BSE) and the environmental secondary electron detector (ESD) of the ESEM. BSE images had moreclearly defined intracellular structures, whereas ESD gave a clearer view of the surface. E. gracilis cells fixed withpotassium permanganate, Spirogyra sp. stained with Lugol's solution, and Saprolegnia sp. fixed with osmium



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tetroxide were compared using BSE and ESD to demonstrate that cellular details could be enhanced by theintroduction of heavy metals. The effect of cellular water on signal quality was evaluated by comparing hydratedto critical point dried specimens.

260 L.M. Egerton-Warburton, B.J. Griffin, and J. Kuo Microanalytical studies of Metal Localization inBiological Tissues by Environmental SEM. Microscopy Research and Technique 25:406-411

Key Words: Bulk frozen hydrated samples, Eucalyptus, Aluminum, Manganese

Abstract: The presence and distribution of Al and Mn in floral and seed tissues of eucalyptus from Al-contaminated soils was analyzed using energy-dispersive X-ray microanalysis (EDS) in an environmental scanningelectron microscope (ESEM). EDS by ESEM determined the distribution of elements between tissue types wassuitable for intact samples or those with lower available moisture or intact specimens. The analytical techniquewas not appropriate for highly vascular samples. Other factors influencing the detection of elements within thetissues. EDS-detectable levels were significantly correlated with tissue concentrations determined by atomicabsorption spectrophotometry for Mn but not for Al.

261 P.J.R. Uwins, M. Murray, and R.J. Gould Effects of Four Different Processing Techniques on theMicrostructure of Potatoes: Comparison with Fresh Samples in the ESEM Microscopy Research andTechnique 25:413-418

Key Words: Potato microstructure, Freeze-substitution, Chemical fixation, Fresh unprocessed potato samples

Abstract: Four common scanning electron microscope (SEM) processing techniques involving freeze-substitution and chemical fixation were compared with fresh unprocessed samples imaged in an environmentalscanning electron microscope (ESEM) using small pieces of potato tubers as test specimens. Potato tubers werechosen for this investigation because of their high moisture content and, consequently, the common need forextensive processing for conventional, high vacuum SEM imaging. ESEM results showed that the freshunprocessed specimens were essentially unaltered, showing clear potato cell structure, morphology, and cellcontent. However, processed networks of material stretching across the surface of cells. These structures mayrepresent fibrillar material or may be artifact caused during processing. Chemical fixation almost entirelydestroyed the microstructure of these potato samples.

262 L.C. Gilbert and R.E. Doherty, Using ESEM and SEM to compare the Performance of Dentinconditioners Microscopy Research and Technique 25:419-423

Key Words: Environmental Scanning Electron Microscope, Smear Layer, Dentin Bonding, Tenure, ScotchBond 2, Syntax, Universal Bond 3, Teeth, Dentistry, Adhesion

Abstract: A comparison of four dentinal conditioners was performed utilizing a traditional scanningelectron microscope (SEM) and the new technology, the ElectroScan environmental scanning electronMicroscope(ESEM Both ESEM and SEM analysis verified current theorized mechanisms of adhesion to dentinsurfaces look like. Increases in information from the "surfaces" of uncoated specimens and the reduction inspecimen preparation time were associated with ESEM analysis.

263 S.L. Geiger, T.J. Ross, and L.L. Barton Environmental Scanning electron Microscope (ESEMEvaluation of Crystal and Plaque Formation Associated with Biocorrosion Microscopy Research andTechnique 25:429-433

Key Word: Biocorrosion, Sulfate-reducing bacteria, Biofilm, Desulfovibrio, Electron microscopy

Abstract: The biofilm attributed to Desulfovibrio vulgaris growing in the presence of ferrous metals wasexamined with an environmental scanning electron microscope. This novel microscope produced images of ironsulfide colloids and other iron containing structures that had not been reported previously. A plaque composed ofiron sulfide enveloped the surface of the corroding metal while crystals containing magnesium, iron, sulfur, andphosphorus were present in the culture where corrosion was in progress. A structure resembling the tubercule



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found in aerobic corrosion was observed on stainless steel undergoing biocorrosion and the elements present in thisstructure included sulfur, iron, chloride, calcium, potassium, and chromium.

264 L.F. Keyser and Ming-Taun Leu, Morphology of Nitric Acid and Water Ice Films MicroscopyResearch and Technique 25:434-438

Key Words: ESEM, Surface reaction, Polar stratospheric clouds

Abstract: Ice films have been used to simulate stratospheric cloud surfaces in order to obtain laboratorydata on solubility’s and heterogeneous reaction rtes. to obtain intrinsic uptake and surface reaction probabilitieswhich can be applied to atmospheric models, it is necessary to carefully characterize these films. In the presentstudy, environmental scanning electron microscopy (ESEM) is used to study thin films of both water ice and nitricacid ice near the composition of the trihydrate. The ices are formed by vapor deposition onto aluminum orborosilicate-glass substrates cooled to about 200º K. Micrographs are recorded during the deposition process andduring subsequent annealing at higher temperatures. The results show that the ice films are composed of looselyconsolidated granules, which range from about 1 to 20 am in size at temperatures between 197º and 235º K. Cubicwater ice is sometimes observed at 200º K and converts to the hexagonal from at slightly higher temperatures. Theloose packing of the granules confirms the high porosity’s of slightly higher temperatures. The loose packing ofthe granules confirms the high porosity’s of these films obtained from separate bulk porosity measurements.Average surface areas calculated from the observed granule sizes range from about 0.2 to 1m 2g-1 and agree withsurface are obtained by gas-adsorption (BET) analysis of annealed ice films. For unannealed films, the BET areasare about an order or magnitude higher than the ESEM results and imply that the unannealed ices containmicroporosity which is lost during the annealing process. The present results have important implications for theextraction of intrinsic reaction probabilities from laboratory rate data.

265 H.E. Nuttall and R. Kale, Application of ESEM to Environmental Colloids Microscopy Research andTechnique 25:439-446

Key Words: Microscopy, Groundwater, Pollution, Radioactive Waste, Transport, Remediation

Abstract: Environmental colloids are toxic or radioactive particles suspended in ground or surface water.These hazardous particles can facilitate and accelerate the transport of toxicants and enhance the threat to humansby exposure to pathogenic substances. The chemical and physical properties of hazardous colloids have not beenwell characterized nor are there standard colloid measurement of their size distribution, zeta potential, chemicalcomposition, adsorption capacity, and morphology. The environmental scanning electron microscope (ESEM) byElectroScan, Inc., analyzes particle sizes, composition, and morphology. It is also used in this study to identify theattachment of colloids onto packing or rock surfaces in our development of a colloid remediation process.

The ESEM has confirmed the composition of groundwater colloids in our studies to generally the samematerial at the surrounding rock. The morphology studies have generally shown that colloids are simply smallpieces of the rock surface that has exfoliated into the surrounding water. However, in general, the source andchemical composition of groundwater colloids is site dependent. We have found that an ESEM works best as avaluable analysis tool within a suite of colloid characterization instruments.

266 Hyung-Min Choi and J.P. Moreau, Oil Sorption Behavior of Various Sorbents Studied by SorptionCapacity Measurement and Environmental Scanning Electron Microscopy Microscopy Researchand Technique 25:447-455

Key Words: Cotton, Milkweed, Kapok, Polypropylene, Biocomponent fiber, Biconstituent fiber, Adsorption,Absorption, Capillary action

Abstract: Oil sorption capacities of various natural and man-made fibrous sorbents were compared in asimulated seawater bath containing oil. Natural sorbents such as milkweed, kapok, cotton, and wool showedhigher sorption capacities than man-made sorbents such as polyester, polypropylene, viscose rayon, nylon 6, nylon66, and acetate. Sorption capacities of the natural sorbent were over 30g oil/g fiber. No definite advantages wereobserved using man-made bicomponent and biconstituent fibers over regular man-made fibers with respect to their



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sorption capacity.Analyses of sorption mechanisms using an environmental scanning electron microscope revealed that an

oil deposit disappeared from the fiber surface after a certain time interval in milkweed, kapok, and cotton. Thissuggested the sorption of oil in these fibers occurred through capillary action, probably due to their hollow lumens.contrarily, adsorption, a surface phenomenon, would be the most prominent mechanism for oil sorption of woolfibers due to large amounts of surface wax, irregular scaly surfaces, and crimp. Effects of both adsorption andabsorption were shown in the oil sorption of man-made fibers, depending upon the type and shape of the sorbent.Dumbbell like oil deposits were seen on the fiber surface in certain oleophilic man-made fibers, because of a partialwetting of oil on the fiber surface. For some hydrophilic man-made fibers such as polyvinylalcohol and copolymerof isobutylene-maleic anhydride, the physical configuration of the fiber was a decisive factor in determining oilsorption capacity of the sorbents.

267 Chao Lung Hwang, Ming Liang Wang, and Shuke Miao Proposed Healing and ConsolidationMechanisms of Rock Salt Revealed by ESEM Microscopy Research and Technique 25:456-464

Key Words: Crushed rock salt, ESEM, Deformation, Healing mechanism, Consolidation mechanism

Abstract: The grain boundary heading behavior of crushed rock salt was mainly studied by employing theenvironmental scanning electron microscope (ESEM) to study the consolidation mechanism of rock salt backfill.Dedicated miniature round rock salt specimens were prepared for observation of the water trappein effect by usinga cold stage in the ESEM to reach saturation conditions. Comparable high pressure pellets were prepared formeasuring the crystal growth. Consolidation tests using materials made at different pressures and containingdifferent moisture levels were conducted in order to construct the proposed mechanism. Direct observation ofspecimens in the ESEM resulted in viewing water trapped on the surface and the formation of a water meniscusbetween two particles. The concentration of brine at the grain boundary was observed as contributing to theamount of recrystallization process may be redrawn. The amount of water therefore has a great effect on theconsolidation of rock salt and is possibly due to the sliding rotation, or crushing of the contact zone of the granularmaterial. From such a study, tentative healing and consolidation mechanisms can be deduced.

268 P.J.R. Uwins, J.C. Baker, and I.D.R. Mackinnon Imaging Fluid/Solid Interactions in HydrocarbonReservoir Rocks Microscopy Research and Technique 25:465-473

Key Words: ESEM, Liquid hydrocarbons, hydrocarbon reservoirs, Clay minerals, Chlorite, Illite/smectite,Calcite, Fluid sensitivity

Abstract: The environmental scanning electron microscope (ESEM) has been used to image liquidhydrocarbons in sandstone’s and oil shales. Additionally, the fluid sensitivity of selected clay minerals inhydrocarbon reservoirs was assessed via three case studies: HCI acid sensitivity of authigenic chlorite in sandstonereservoirs, freshwater sensitivity of authigenic illite/smectite in sandstone reservoirs, and bleach sensitivity of avolcanic reservoir containing abundant secondary chlorite/corrensite. The results showed the suitability of usingESEM for imaging liquid hydrocarbon films in hydrocarbon reservoirs and the importance of simulating in situfluid-rock interactions for hydrocarbon production programs. In each case, results of the ESEM studies greatlyenhanced prediction of reservoir/borehole reactions and, in some cases, contradicted conventional wisdomregarding the outcome of potential engineering solutions.

269 P.W. Brown, J.R. Hellmann, and M. Klimkiewicz, Examples of Evolution of Microstructure inCeramics and Composites Microscopy Research and Technique 25:474-486

Key Words: Coatings, Copper thick films, Crystallization, Hydroxyapatite, Propellants

Abstract: In this article we describe a number of studies involving the direct observation of microstructuralevolution. In general these investigations were carried out to establish the mechanistic paths involved. Thematerials studied range from fibers being evaluated for use in high temperature ceramic composites to energeticmaterials used as propellants. In particular we discuss the room temperature imaging of materials difficult toimage by conventional means and the use of the chamber atmosphere to influence microstructural evolution.



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Imaging of hydroxyapatite formed by chemical means is briefly described as an example of a difficultmicrostructure. Microstructural evolution during calcium aluminate cement hydration relies on the chamberatmosphere to control moisture loss from the hydrating specimens. In some instances microstructural evolutionwith heating occurred independently of the chamber atmosphere. Grain growth in PZT films formed by sol-gelprocesses depends strongly on temperature but does not appear to depend on the chamber atmosphere. This is alsothe case for the combustion of nitroamine propellants in that their combustion’s does not depend on access to anindirect role in determining microstructure. However, the mechanistic path driving microstructural evolution incopper-based inks used as conductive paths on electronic substrates is atmosphere dependent. These inks areformulated from copper powder, glass, and an organic binder, and the interaction of the binder with an oxidizingatmosphere allows it to be butted out before significant interaction occurs between the copper powder and the glass.Finally, the microstructural variations during the oxidation of structural composites at high temperature were usedto allow assessments of their likely failure mechanisms.

270 E.R. Prack, An Introduction to Process Visualization Capabilities and Considerations in theEnvironmental Scanning Electron Microscope (ESEM) Microscopy Research and Technique 25:487-492

Key Words: Non-destructive techniques, SEM, FE-SEM

Abstract: Process visualization can be a very powerful tool for understanding dynamic processes. Processvisualization requires a non-destructive inspection will be described and compared. The applicability of these non-destructive inspection methods to process visualization will be compared and contrasted. Particular attention willbe paid to a recent development in this area, the environmental scanning electron microscope (ESEM) which isinherently a non-destructive inspection technique with the advantages of electron microscopy for superiormagnification and depth of field capability. The ESEM offers a unique platform for process visualization studies.The majority of process visualization is currently done using optical microscopes with hot stages for observingmorphological effects top down (optical microscopes) or from the side (contact angle). Major limitations of theseoptical methods include lack of magnification, poor depth of field, and clouding of optics.

Process visualization is best carried out utilizing a non-destructive technique, such as the ESEM, sinceinvasive sample preparation techniques such as conductive coatings alter the sample and make interpretation moredifficult. Common process variables such as thermal profiling and the effect of ambient conditions have beenexamined using the ESEM. Other process variables that could be of interest in the future will be discussed. Thereare limitations in the ability of the ESEM to reproduce actual process conditions, such as pressure and mass flowrate trade-offs. The ESEM can also be combined directly and indirectly with other analytical techniques todetermine the composition of the sample and/or by products of a reaction that is being monitored.

This paper will serve as an overview and introduction for several papers which deal in depth with specificprocess visualization applications which utilize the ESEM. A series of illustrative examples of previous work willbe referenced and briefly discussed. The examples will emphasize the importance of non-destructive testingtechniques in material science and semiconductor applications. The application window of the ESEM for processvisualization will be explored, including trade-offs in process conditions that can be examined. Observation ofdynamism processes include examples such as corrosion studies of various materials such as stainless steel andthermal studies of industrially relevant processes such as ceramic processing, soldering, and sealing.Morphological and compositional process visualization applications will be presented. An example ofmorphological applications observed is solder reflow and inter-metallic formation as a function of the materialsused and the atmosphere during processing. Morphological coupled with compositional applications includemonitoring outgasssing products from solder paste and Ag/glass die attach material.

271 N. Koopman, Application of ESEM to Fluxless Soldering Microscopy Research and Techniques25:493-502

Key Words: Solder joining, Ambient effects, Solder oxidation, Solder microstructure, Solder morphology,Atmosphere effects, Solder



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Abstract: The ESEM is ideally suited to study soldering processes. We have used it to observe solderreflow and joining in ambient gases. It reproduces effects of atmospheric pressure reflow in a hot stage lightmicroscope, but with much better clarity and depth of field. Compared to a regular SEM, the ESEM offersadvantages of atmosphere control and ability to observe the solder samples without carbon or gold coating. Thesecoatings could interfere with the oxidation/reduction reactions which occur at the solder/ambient gas interface.Very thin surface films, especially oxide layers, dramatically influence the flow of liquid solder and the ability ofsolder to wet or join to another surface. Fluxless processes in particular are ideally suited for study in the ESEM.We have used the ESEM to observe dynamic fluxless soldering and have recorded events on videotape for laterstop-action still pictures and slow motion photography. Examples of these processes are shown to illustrate theESEM capability. Included are solder deformation structure, balling reflow of eutectic solder in hydrogen, ballingreflow of eutectic solder in nitrogen, joining of two solder disks in nitrogen, and dynamic melting and freezing ofan off-eutectic dendritic alloy. All of these are observed in the absence of flux.

272 K.W. Kirchner, G.K. Lucey, and J. Geis, Copper/Solder Inter-metallic Growth Studies MicroscopyResearch and Techniques 25:503-508

Abstract: Copper samples, hot solder (eutectic) dipped and thermally aged, were cross-sectioned and placedin and environmental scanning electronic microscope (ESEM). While in the ESEM the samples were heated for~2.5h at 170ºC to stimulate the growth of additional Cu/Sn inter-metallic compound. The intent of the study wasto obtain a continuous real-time videotape record of the diffusion process and compare the observations to staticSEM images reported to represent long-term, naturally aged inter-metallic growth. The video obtained allows theobservation of the diffusion process and relativistic growth phenomena at the Cu, Cu3Sn,Cu6Sn5, and solderinterfaces as well as effects on the bulk Cu and solder. Effects contrary to earlier reports were observed; forexample, growth rates of Cu3Sn were found to greatly exceed those of Cu6Sn5.

Key Words: Inter-metallic compounds, ESEM, SEM

273 T.J. Singler, J.A. Clum, and E.R. Prack, Dynamics of Soldering Reactions: Microscopic ObservationsMicroscopy Research and Technique 25:509-517

Key Words: Metallurgical reactivity, Inter-metallics, Precursor films, Surface energy

Abstract: This paper provides a summary of some in situ, high-resolution studies of solder spreadingreactions on microelectronic circuit metallizations. Experiments are described that focus on the use of theenvironmental scanning electron microscope, or ESEM. Those experiments have been complemented by studiesusing optical hot-stage microscopy and have been supplemented by additional analytical tools such as energydispersive x-ray microanalysis, Auger and ESCA to evaluate chemical processes. Two general results fromdynamic scanning electron microscope observations are that 1) molten solder alloys undergo a segregation processduring spreading in which a "precursor" film spreads in advance of the bulk solder and 2) the spreading front,which may be enriched in Sn from Pb-Sn or Bi-Sn solders, or in from Pb-In solders, spreads along high-reactivityfeatures of the metallization surface as a reacting "precursor" film. A third observation from these tests is that, inunconfined geometries, the reactive metallization, if not sufficiently thick, can be dissolved by the solder beforewetting is complete, leading to de-wetting of the solder. Both the kinetics and extent of spreading of these filmsand the relationship of these phenomena to the commonly measured contact angle and wetting forces are currentlybeing examined by a range of complementary techniques. Information gathered in these studies shows that processtemperature as well as composition, reactivity, and relative amounts of the solder and metallization species shouldall be factors of interest to the those responsible for control of soldering process.

274 L.F. Link, W.R. Gerristead, JR., and S. Tamhankar, Copper Thick Film Sintering Studies in anEnvironmental Scanning Electron Microscope Microscopy Research and Technique 25:518-522

Key Words: ESEM, Sintering, Copper, Thick film

Abstract: The significance of the ElectroScan environmental scanning electron microscope (ESEM) as aprocessing tool from studying dynamic morphological changes under controlled temperature/atmosphere



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conditions was evaluated. The ability to observe dynamic processes in situ, which cannot be achieved by othermeans, is critical to understanding microstructural formation.

Processing of printed copper thick films on ceramics was used as a test case, wherein morphologicalchanges associated with the steps of organic binder removal and sintering of copper particles wereobserved/examined in real time. Good agreement was seen between microstructures obtained in the ESEM andthose achieved in a belt furnace when similar process variables were used. When processed in atmospheres whichwere proven to induce sintering in a conventional belt furnace, tapes in real time. Determination of critical eventtemperatures was achieved-that is, binder burnout occurring between 270° and 350°C, onset of oxidation at 520°C,and sintering starting at 770°C.

It was thus verified that the microstructural changes during the copper thick film sintering process can beobserve in situ using an ESEM.

275 W.R. Gerristead, , L.F. Link, R.C. Paciej, P. Damiani, and H. Li, Environmental Scanning ElectronMicroscopy for Dynamic Corrosion Studies of Stainless Steel Piping Used in UHP Gas DistributionSystems Microscopy Research and Technique 25:523-528

Key Words: ESEM, In situ, Microelectronics, Stainless steel tubing

Abstract: An ElectroScan ESEM was used for in situ corrosion studies on cold drawn electropolished 316Lstainless steel tube surfaces in the as-received and passivated conditions. Corrosion product was removed as itformed and the tube surface was viewed before, during, and after corrosive attack. The corrosion process wasfollowed in situ, and the sample features most susceptible to corrosion (draw lines, inclusions, etc.) were identified.In addition, X-ray photoelectron spectroscopy (XPS) was used to study the changes in surface chemistry aftercorrosive attack. This information provided clear evidence of relevant corrosion mechanisms and relativecorrosion susceptibility.

276 G.D. Danilatos, Bibliography of Environmental Scanning Electron Microscopy Microscopy Researchand Technique 25:529-534

Key Words: ESEM, Survey of ESEM. Review of ESEM, Development of ESEM, Uses of ESEM, Applicationsof ESEM

Abstract: Two updated lists of publications on environmental scanning electron microscopy are complied.One list contains mainly with the applications of the technique. A brief introductory summary of the field ispresented.

277 B. Caveny, Cement Hydration Study Using the Environmental Scanning Electron MicroscopeICMA Proceedings

Key Words: cement

Abstract: This paper will detail a brief study of hydrating cement using the ESEM.The ESEM is capable of working at much higher pressures than conventional SEM, thus allowing wet samples tobe examined in a more natural environment.A class H oil well cement will be studied in several degrees of hydration’s and ESEM photomicrographs will beshown of the various microstructures observed.

278 Robert Pope and Raymond W. Scheetz, Dynamic Events Related to Humidity Changes on BotanicalSamples Imaged with the Environmental SEM, Dept. of Biological Sciences, University of SouthernMississippi, Hattisburg, MS 39406-5018

Key Words: humidity, botanical samples

Abstract:



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279 P.A. Wagner, B.J. Little, R.I. Ray, Investigations of Microbiologically Influenced Corrosion UsingEnvironmental Scanning Electron Microscopy Corrosion ‘92, The National Association of CorrosionEngineers, #185.

Key Words: microbiologically influenced corrosion, ESEM, SEM

Abstract: A newly developed Environmental Scanning Electron Microscope (ESEM) coupled with anenergy dispersive x-ray spectrometer (EDS) was used to characterize the topography and chemical composition ofwet biofilms and corrosion products on metal surfaces in addition to spatial relationships between micro-organisms, substratum and corrosion layers. Case studies are presented to demonstrate the applicability andadvantages ESEM/EDS technology in the investigation of microbiologically influenced corrosion (MIC) ascompared to traditional methods.

280 P.A. Wagner, B.J. Little, R.I. Ray, Biofilms: An ESEM Evaluation of Artifacts Introduced DuringSEM Preparation, Naval Oceanographic and Atmospheric Research Laboratory, Stennis Space Center,MS 39529-5004

Key Words: Biofilm, scanning electron microscope, environmental scanning electron microscope

Abstract: Descriptions of biofilms and their elemental compositions based on scanning electronmicrographs and energy dispersive x-ray analysis cannot be related to the original condition of the biofilms on thesurface. Solvent replacement of water removes extra cellular polymeric material and reduces the concentration ofelements bound within the biofilm. In the wet state, bacteria and micro algae are enmeshed in a gelatinous filmthat is either removed or dried to a thin inconspicuous residue during sample preparation for scanning electronmicroscopy. The Environmental Scanning Electron Microscope (ESEM) provides a fast, accurate image ofbiofilms, their spatial relationship to the substratum and elemental composition.

281 K.-R. Peters, L.A. Firstein, A. Noz, Environmental SEM and Conventional SEM Imaging of Electron-Sensitive Resist: Contrast Quality and Metrological Applications, Micro electric Engineering 17(1992) 455-458 Elsevier Science Publishers B.V.

Key Words: Electron-Sensitive Resist, sub-micron IC’s,

Abstract: State-of-he-art SEM metrological approaches are discussed to elucidate inherent deficiencies thatprevent accurate assessment of image fidelity in the production or inspection of sub-micron IC’s, especially on theresist level. The new technique of Environmental SEM is demonstrated to allow topographic contrast generation,unaffected by surface charging, for SAL-601.

282 Sudhir Mehta, Richard Jones, Cryogenics with Cement Microscopy Redefines Cement Behavior,ARCO Exploration & Production Technology, Oil & Gas Journal, Oct. 3, 1994

Key Words: cement, cryogenics

Abstract:

283 H.S. Kaufman, K.D. Littlemoe, J.T. Mastovich, H.A. Pitt, Environmental Scanning ElectronMicroscopy of Fresh Human Gallstones Reveals New Morphologies of Precipitated Calcium Salts.G.W. Bailey, J. Bentley and J.A. Small, Editors, Proc 50th Annual Meeting of the Microbeam AnalysisSociety and the 19th Annual Meeting of the Microscopial Society of Canada, EMSA, San Francisco Press,1992.

Key Words: gallstones

Abstract: The purpose of this experiment was to study fresh gallstones by Environmental ScanningElectron Microscope (ESEM) to determine if dehydration affects gallstone Ca salt morphology.



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284 A. D’Emanuele, J. Kost, J.L. Hill, R. Langer, An Investigation of the Effects of Ultrasound onDegradable Polyanhydride Matrices., American Chemical Society (1992) Macromolecules 25.

Key Words: ultrasound, polymer erosion

Abstract: In vitro methodology has been developed to investigate the effects of therapeutic ultrasound onpolymer erosion. Enhancement in the rate of polymer erosion was demonstrated using therapeutically acceptablelevels of ultrasound on a model class of degradable polymers—polyanhydrides. It was found that the ultrasoundenhances polymer degradation as demonstrated by the enhanced decrease in polymer molecular weight during theinduction period of erosion. Additionally, morphological changes on the surface of ultrasound exposed deviceswere assessed by Environmental Scanning Electron Microscopy and suggested that cavitation may cause themechanical disintegration of the polymer surface.

285 Wang Peiming, Li Pingjiang, Chen Zhiyuan, Research on the Morphology of Cement Hydrates bySEM, State Key Laboratory of Concrete Materials Research, Tongji University, Shanghai, 200092, China

Key Words: hydrate, morphology, hydration space, environmental pressure

Abstract: This paper throws light on the morphology change of cement hydration products under theobservation of SEM. The results show that the morphologies are changed, some even significantly, with thesample grown within different free space, or under the observation of different vacuum degree to others.

286 Bill Caveny, Gant McPherson, Lance Brothers, Sudhir Mehta, Crystal Phases of Cement Paste Cured inHigh Temperature CO2 Environment

Key Words: geothermal wells

Abstract: Completion of geothermal wells in hostile environments require laboratory studies to determinewhich cement blends might work best for a given set of conditions. This paper details some data obtained fromblends that were cured in CO2 environments at 316°C. XRDA, ESEM and light microscopy and other methodswere used in the analyses.

287 S. Mehta, Imaging of Wet Specimens in Their Natural State Using Environmental Scanning ElectronMicroscope (ESEM): Some Examples of Importance to Petroleum Technology. (1991) Society ofPetroleum Engineers Inc. SPE 22864

This paper was prepared for presentation at the 66th Annual Technical Conference and Exhibition of the Society of Petroleum Engineers held in Dallas, TX, October 6-9,1991.

This paper was selected for presentation by an SPE Program committee following review of information contained in an abstract submitted by the author(s). Contents of thispaper, as presented, have not yet been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does notnecessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at the SPE meetings are subject to publication review bythe Editorial Committee of the Society of Petroleum Engineers. Permission to copy is restricted to an abstract of 300 words, illustrations may not be copied. The abstractshould contain conspicuous acknowledgment of where and by whom the paper is presented.Write Publications Manager, SPE, PO Box 833836, Richardson, TX 75083-3836. U.S.A.



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Key Words: petroleum

Abstract: The barrier to imaging wet or oily specimens in their “native” states in a scanning electronmicroscope known as the Environmental Scanning Electron Microscope (ESEM). With the new features built intoESEM, the need for preparing samples with various specimen-destroying preparation techniques has beeneliminated. For example, wet reservoir rocks can be imaged and analyzed in their “native” state, without drying,freezing or coating with a conductive layer, by saturating the ESEM specimen chamber with water vapor{P

H2o=~0.46 psi [3.2kPa] at 25ºC [77ºF]} during examination. The ESEM also allows dynamic experiments to beperformed in a variety of gases at pressures up to 0.6 psi [4kPa] and temperatures up to 1000ºC.This paper presents the key features of the ESEM which distinguish it from the conventional SEM, and results ofsome ESEM feasibility studies important in petroleum technology such as matrix acidization, water flooding, andclay and cement hydration. The results indicate that the ESEM combined with the energy-dispersive x-rayspectroscopy is a powerful new technique capable of providing a new understanding of many exploration andproduction related studies not previously possible with conventional “high-vacuum” SEM microscopy.

288 A.B.M. Simanjuntak, P.T. Caltex, L.L. Haynes, ESEM Observations Coupled With Coreflood TestsImprove Matrix Acidizing Designs, (1994) Society of Petroleum Engineers Inc.

This paper was prepared for presentation at the SPE Int’l Symposium on Formation Damage Control held in Lafayette, Louisiana, 7-10 February 1994.

This paper was selected for presentation by an SPE Program committee following review of information contained in an abstract submitted by the author(s). Contents of thispaper, as presented, have not yet been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does notnecessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at the SPE meetings are subject to publication review bythe Editorial Committee of the Society of Petroleum Engineers. Permission to copy is restricted to an abstract of 300 words, illustrations may not be copied. The abstractshould contain conspicuous acknowledgment of where and by whom the paper is presented.Write Librarian, SPE, PO Box 833836, Richardson, TX 75083-3836. U.S.A.

Key Words: acid, core flood tests,

Abstract: A new laboratory procedure has been developed to study formation damage mechanisms andimprove acid stimulation designs using an Environmental Scanning Electron Microscope (ESEM) coupled withcore flood tests. An ESEM has the unique capability of observing a sample wet or dry, in its natural, uncoatedstate. The core plugs used in core flooding experiments can be observed at the same locations, before during andafter treatment with workover and completion fluids, without any cleaning, drying or metal coating processes. Thedirect effects of the simulation and completion fluids on the formation minerals can be seen along with anychanges to the initial porosity. The ESEM is combined with energy-dispersive x-ray spectroscopy (EDS) to allowelemental analysis of precipitates or observation of changes in the elemental composition of the clay minerals.

289 L.L. Haynes, ESEM: An emerging Technology for Determination of Fluid/Rock Interactions inHydrocarbon Production., (1991) Texaco, EPTM TM# 91-186.

Key Words:

Abstract: At Texaco’s Exploration and Production Technology Department in Bellaire, TX, research isbeing conducted on core material using the Environmental Scanning Electron Microscope (ESEM). In the past,conventional SEM’s have proven to be a very useful tool for describing reservoir rocks. They are capable ofproviding details at a sub-micron scale thus revealing rock characteristics which aid in the understanding of thecomplex diagnetic* history and petrographic# properties of the rock. The ESEM allows these petrographic studiesto go one step further. Because of its specialized design, the ESEM allows viewing of any sample, wet or dry, in itsnatural state. Also a microinjection port allows water and other fluids to be placed directly on the sample duringimaging. Dynamic events such as dissolution and precipitation can be observed in real-time and recorded throughthe use of a VCR.

* Diagnosis refers to all of the physical, chemical and biological changes that a sediment is subjected to after a grain has been deposited but before itis metamorphosed.# Petrographic properties are rock properties described in hand specimen and thin section analysis.



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290 P.J.R Uwins ESEM: Environmental Scanning Electron Microscopy EIX 95-17 EIX95172606357NDN - 017-0224-8612-8 (1994) Materials Forum v18 p51-75

Key Words:

Abstract: The Environmental Scanning Electron Microscope (ESEM) is one of the most exciting newdevelopments in the field of Electron Microscopy. The ESEM differs from conventional Scanning ElectronMicroscopes (SEM) by being able to examine materials including liquids and oils in their natural state with noprior sample preparation. Accessory equipment, cooling, heating and manipulating devices allow themanipulation of samples thus making it possible for the first time to image dynamic processes such as wetting,drying, absorption, corrosion, melting, crystallization, curing and fracturing at high magnification. (Authorabstract) 24 Refs.

291 J.E. Johnson Microscopy Research and Technique, Volume 25, Numbers 5 and 6, August 1993, WileyLiss, A John Wiley & Sons, Inc., Publication.

Edward M. Griffith III and G.D. Danilatos Foreword

G.D. Danilatos Introduction to the ESEM Instrument

291a Robin E. de la Parra, A Method to Detect Variations in the Wetting Properties of MicroporousPolymer Membranes

291b Paul Messier and Timothy Vitale, Cracking in Albumen Photographs: An ESEM Investigation

291c James H. Rask, John E. Flood, John K. Borchardt, and Greg A. York, The ESEM Used to ImageCrystalline Structures of Polymers and to Image Ink on Paper

291c Scott A. Wight and Cynthia J. Zeissler, Environmental Scanning Electron Microscope ImagingExamples Related to Particle Analysis

291d Scott P. Collins, Robert K. Pope, Raymond W. Scheetz, Richard I. Ray, Patricia A. Wagner, and Brenda J.Little, Advantages of Environmental Scanning Electron Microscopy in Studies of Microorganisms

291e Louise M. Egerton-Warburton, Brendon J. Griffin, and John Kuo, Microanalytical Studies of MetalLocalization in Biological Tissues by Environmental SEM

291f Philippa J.R. Uwins, Margaret Murray, and Robert J. Gould, Effects of Four Different ProcessingTechniques on the Microstructure of Potatoes: Comparison With Fresh Samples in the ESEM

291g Lynn C. Gilbert and Robert E. Doherty, Using ESEM and SEM to Compare the Performance ofDentin conditioners

291h Karen Hoyberg and Kenneth G. Kruza, Application of Environmental Scanning Electron Microscopyin the Development of Detergents and Personal Products

291I Steve L. Geiger, Timothy J. Ross, and Larry L. Barton, Environmental Scanning Electron Microscope(ESEM) Evaluation of Crystal and Plaque Formation Associated With Biocorrosion

291j Leon F. Keyser and Ming-Taun Leu, Morphology of Nitric Acid and Water lee Films

291k H.E. Nuttall and Rahul Kale, Application of ESEM to Environmental Colloids

291l Hyung-Min Choi and Jerry P. Moreau, Oil Sorption Behavior of Various Sorbents Studied by SorptionCapacity Measurement and Environmental Scanning Electron Microscopy

291m Chao Lung Hwang, Ming Liang Wang, and Shuke Miao, Proposed Healing and ConsolidationMechanisms of Rock Salt Revealed by ESEM



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291n Philippa J.R. Uwins, Julian C. Baker, and Ian D.R. Mackinnon, Imaging Fluid/Solid Interactions inHydrocarbon Reservoir Rocks

291o P.W. Brown, J.R. Hellmann, and M. Klimkiewicz, Examples of Evolution of Microstructure inCeramics and Composites

291p Edward R. Prack, An Introduction to Process Visualization Capabilities and Considerations in theEnvironmental Scanning Electron Microscope (ESEM)

291q Nick Koopman, Application of ESEM to Fluxless Soldering

291r Kevin W. Kirchner, George K. Lucey, and James Geis, Copper/Solder Inter-metallic Growth Studies

291s Timothy J. Singler, James A. Clum, and Edward R. Prack, Dynamics of Soldering Reactions:Microscopic Observations

291t Leslie F. Link, William R. Gerristead, Jr., and Satish Tamhankar, Copper Thick Film Sintering Studiesin an Environmental Scanning Electron Microscope

291u W.R. Gerristead, Jr., L.F. Link, R.C. Paciej, P. Damiani, and H. Li, Environmental Scanning ElectronMicroscopy for Dynamic Corrosion Studies of Stainless Steel Piping Used in UHP Gas Distribution Systems

291v G.D. Danilatos, Bibliography of Environmental Scanning Electron Microscopy



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292 Junhui Li; Pecht, M. Engel, P. A.; Chen, W. T., Dynamic investigation of thermal and sorptive effectson electronic packages -

Key Words: microscopes; scanning electron

Abstract: Temperature and relative humidity affect electrical, chemical, mechanical, and thermo-mechanical properties of microelectronic packages. Attention has been focused on the environmental effects thatresults in various physical failures. The scanning electron microscope is, a useful tool for visually characterizingthese failures, but its use is restricted because the specimens examined must be coated. The environmentalscanning electron microscope functions like a traditional high-quality scanning electron microscope, and alsoallows the researcher to examine unprepared, uncoated specimens. This makes it possible to view wet or moistspecimens in their natural states. In this paper, several experimental efforts using the E-SEM technique arediscussed. The first was a study of thermal effects on L-band microwave monolithic integrated circuits. Thesecond investigation concentrated on ad/absorptive effects an multi layer thin film polymides. The third studyfocused on thermal and humidity cycling effects on the interfacial bonding characteristics of resin-fiber interfacesnear plated-through-holes in printed wiring boards.

293 Read, 0. T.; Dally, J. W. EDITOR- Engel, P. A.; Chen, W. T., Local strain measurement by electronbeam moiré -Proceedings of the 1993 ASME International Electronics Packaging Conference New York,NY, USA)

Key Words: microscopes; scanning electron

Abstract: Moiré fringe patterns can occur when high-frequency line arrays are observed in the scanningelectron microscope. We have applied this phenomenon to local deformation measurement in a glass-fiber-reinforced plastic and in a plated-through-hole. In the GFRP, local strain measurements were made by interpretingthe moiré fringe patterns over gage lengths from 10 to 30 mum at a 0-90 ply interface during tensile testing. Loadshedding by the transverse ply was evident from the fringe patterns. On a cross section of a plated-through-hole,inhomogenous strains were observed.

294 Bong Mo Park; Su Jin Chung, Optical, electron microscopic, and X-ray topographic studies of ferroicdomains in barium titanate crystals grown from high-temperature solution -Journal of the AmericanCeramic Society (USA) VOL. 77 NO. 12 Dec. 1994 PP. 3193-201 31 references) Copyright 1995.

295 V.N.E. Robinson, ,B.W. Robinson , Materials Characterization in a Scanning Electron MicroscopeEnvironmental Cell, Scanning Electron Microscopy, Vol. 1, SEM Inc., AMF O’Hare IL 60666, USA .

Key Words: Backscattered Electron Detector, Environmental Cell, Specimen Charging, Atomic numbercontrast, Materials Characterization

Abstract: The combination of scanning electron microscope, environmental cell modification and energy-dispersive X-ray detector has been employed, as a system, in materials characterization. The system requires nospecimen preparation, produces images which display high atomic number contrast together with good topographycontrast, and enables different phases, detected by their atomic number contrast, to be quickly identified by X-rayanalysis. The lack of specimen preparation means that analysis can be extremely rapid, with time periods as shortas one minute being achieved for receiving. imaging and analyzing the specimen.

296 P.T. Miller, S.A. Farrington, L. Kovach, Petrographic Thin-section and Scanning ElectronMicroscope Analysis of a Mortar Fabricated in a Microgravity Environment: Preliminary Studies.,Master Builders Inc.

Key Words



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Abstract: A Portland cement mortar was mixed onboard a recent space shuttle mission to study the effectsof a microgravity environment on the production of a hardened mortar. A control sample was subsequentlyprepared in the same mixer under gravity conditions on the earth’s surface. The purpose of this study is theexamination of the cement paste microstructure to determine the effects of microgravity on its development.Optical microscopy of thin sections of mortar and scanning electron microscopy of fracture surfaces of mortar werechosen for the analysis. Thin-section analysis suggested that the extent of aggregation of the calcium hydroxidecrystals was less under the influence of microgravity. Scanning electron microscopy suggested that themicrogravity allowed for the formation of a microstructure with a much more distinct void structure.

297 U. Landman, R. Nieminen, Computational Materials Science, Volume 2, No. 2, March 1994, Commat 2(2) 213-412 (1994).Elsevier, ISSN 0927-0256

Key Words:

Abstract:

297a A. Mahmoudi, B. Soudini, N. Amrane, B. Khelifa and H. Aourag Conduction bond edges chargedensities in Cdx Zn1-x S.

297b J. Kohanoff Phonon spectra from short non-thermally equilibrated molecular dynamics simulations

297c D. Bourbie and K. Driss-Khodia Transport of electronic excitations in disordered systems

297d J. Hutter, H.P. Lothi and M. Parrinello Electronic structure optimization in plane-wave-based densityfunctional calculations by direct inversion in the iterative subspace

297e Y. Xi, T.B. Bergstrom and H.M. Jennings Image intensity matching technique: Application to theenvironmental scanning electron micro-scope

297f K. Kokko, P.T. Salo and K. Mansikka First principles study of the solute atom induced latticedistortion effects on bulk modulus and band structure in Li-alloys

297g A. Fischer and A. Pyzalla-Schieck Calculation of thermal micro residual stresses in materialscontaining coarse hard phases

297h D. Faken and H. Johnsson Systematic analysis of local atomic structure combined with 3D computergraphics

297i M. Driz, N. Bodi, B. Soudini, N. Amrane, H. Abid, N. Bouarissa, B. Khelifa and H. Aourag The alloyingand pressure dependence of band gaps in GaAs and GoAsxP1-x

297j M. Sluiter Introducing distant interactions in the cluster variation method

297k Chen Haoran, Yang Quangsan and F.W. Williams A self-consistent finite element approach to theinclusion problem

297l M.J.W. Greuter and L. Niesen Molecular dynamics simulation of the lattice dynamics of solid Kr

297m V. Vydra, K.M.A. El-Kader and V. Ch6b Influence of variations of temporal pulse shape in excimerlaser processing of semiconductors

297n L.-W. Wang and A. Zunger Large scale electronic structure calculations using the Lanczos method

297o C.S. Wu and L. Dorn Computer simulation of fluid dynamics and heat transfer in full-penetratedTIG weld pools with surface depression



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297p P.H. Lambin, L. Philippe, J.C. Charlier and J.P. Michenaud Electronic band structure of multilayeredcarbon tubules

297q H.-J. Unger Theory of vacuum tunneling and its application to the scanning tunneling microscope

297r H. Nara, T. Kobayasi, K. Takegahara, M.J. Cooper and D.N. Timms Optimal number of directions inreconstructing 3D momentum densities from Compton profiles of semiconductors

297s G. Tichy Interaction potentials in metals

297t J. Kudrnovski, V. Drchal, S.K. Bose, 1. Turek, P. Weinberger and A. Posturel Electronic properties ofrandom surfaces

297u A. Qteish, R.J. Needs and V. Heine Polarization, structural and electronic properties of SiC polytypes

297v A. Qteish and R.J. Needs Ab-initio pseudo potential calculations of the valence band offset atHgTe/CdTe, HgTe/InSb and CdTe/InSb interfaces: transitivity and orientation dependence

297w A. Muhoz and K. Kunc New phases and physical properties of the semiconducting nitrides: AIN,GaN, InN

298 V. N. E. Robinson, The SEM Examination of Wet Specimens, SCANNING Vol. 1, 149-156 (1978), G. Witzstrock Publishing House Inc., Received: July 24, 1978, Faculty of Applied Science, The Universityof New South Wales, P. 0. Box 1, Kensington, N.S.W., 2033, Australia

Key Words:

Abstract: The natural state of biological specimens is hydrated at temperatures above 0°C. Thesespecimens cannot be placed directly into a conventional SEM because the water would vaporize and interfere withthe electron generation and/or detection systems. To overcome this problem, a number of dehydration techniqueshave been developed, including air drying, critical point drying (Anderson 1951, 1956) (reviewed by Cohen 1977)and freeze drying from water or non aqueous solutions (Boyde 1974, de Harven et al 1977). These techniqueshave enabled many specimens to be examined -whilst retaining a shape somewhat similar to their originalstructure. However, they do not prevent dimensional distortion during dehydration and quite large volumereductions can still occur (Boyde 1976, Boyde et al 1977). Also, the surface appearance of many samples can beradically altered by the different dehydration techniques employed.

The best method of overcoming these distortions during dehydration is to avoid dehydration. Two separatetechniques have been developed to enable hydrated specimens to be examined in an SEM. The first involveslowering the vapor pressure) freezing the specimen in liquid nitrogen or liquid nitrogen cooled freon (Echlin et al1970, Echlin 1971, Nei et al 1973, Robinson 1975b). Freezing prevents the vapor from interfering with theelectron generation and detection systems, provided sufficiently low temperatures are reached and maintainedduring examination. These techniques enable a large range of specimens to be successfully examined withoutdehydration, although they have some limitations, including the possibility of ice crystallization damage.

However, the natural state of biological specimens is not frozen and it is desirable to examine many specimens intheir natural state and/or in contact with water.



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The second major technique of examining hydrated specimens is to examine them in an environmental cell,which isolates the high water vapor pressure from the electron generation and detection equipment. This paperdiscusses the various methods of performing this isolation and the factors which limit their performance.

299 V.N.E. Robinson , Facility of Applied Science, University, of New South Wales, PO Box 1, Kensington,N.S. W., 2033, Australia, A simple technique for examining frozen hydrated specimens in thescanning electron microscope, Journal of Microscopy, Vol. 104, Pt 3, August 1975, pp. 287-292.

Key Words:

Abstract: The use of a wide angle backscattered electron detector in a scanning electron microscope, whichhas the capability of the specimen chamber pressure being controlled independently of the column pressure,provides a simple technique for examining frozen hydrated specimens. Large specimens have been examinedwithin 1 min. of being placed on the stub and have been examined for many hours without charging artifacts ordistortion due to dehydration.

300 V.N.E. Robinson , Facility of Applied Science, University, of New South Wales, PO Box 1, Kensington,N.S. W., 2033, Australia, A wet stage modification to a scanning electron microscope, Journal ofMicroscopy, Vol. 103, Pt 1, January 1975, pp. 71-77.

Key Words:

Abstract: A modification to the vacuum system of a JSM2 scanning electron microscope has enabledhydrated specimens to be placed inside the chamber of the instrument and to be surrounded by water vapor at apressure up to approximately 1.3kPa (10 Torr). The surface topography was observed by detecting thebackscattered electrons using a wide angle backscattered electron detector placed close to the specimen. Themicroscope was operated in the normal scanning mode which allowed the examination of the surface topography ofthe specimens, whilst still retaining the depth of focus which is a feature of the SEM. This modification hasenabled resolution of approximately 0.2µm to be obtained from biological specimens partially immersed in waterat temperatures just above 0°C.

301 Todd Bruce Bergstrom, An Environmental Scanning Electron Microscope (ESEM) Investigation ofDrying Cement Paste: Drying Shrinkage, Image Analysis, and Modeling. Northwester University,Evanston IL, USA, December 1993, © 1993 T.B. Bergstrom

Key Words:

Abstract: The Environmental Scanning Electron Microscope (ESEM) and new image analysis techniquesare used to document the microstructure of cement pastes. The ESEM is shown to be vital to the imaging ofcement hydration products at early age. An image intensity matching technique, which computes deformationbetween images with a resolution of 0.1%, is used in conjunction with the ESEM. This technique is used todocument drying shrinkage, which is defined as the length change associated with loss of water. The effects ondrying shrinkage of w/c, curing temperature, age, and drying rate are investigated. The magnitude of shrinkage isshown to vary as a function of scale, from individual particles to an area or average behavior. Shrinkage is shownto be controlled by both microstructure and hydration product properties. W/C is shown to vary the microstructurewhile curing temperature, age, and drying rate affect the properties of the hydration products. Experiments andmodeling show there are restraining effects from calcium hydroxide and hydrous cement that accounts fordifferences in shrinkage between single particle and average behavior. Modeling is also used to demonstrate that acement paste shrinks more at older ages when normalized by the shrinkage of the calcium silicate hydrate andporosity. Experimental results form the basis for a more complete understanding of the (micro)structure-propertyrelationships for cement paste.

302 R.E. Cameron and A.M. Donald, Minimizing Sample Evaporation In the Environmental ScanningElectron Microscope, Polymers and Colloids Group, Cavendish laboratory, Madingley Road, Cambridge,CB3 OHE, United Kingdom



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Key Words: Environmental Scanning Electron Microscope (ESEM), evaporation, condensation, pumpdownprocedure

Abstract: The ElectroScan Environmental Scanning Electron Microscope (ESEM) enables the observationof wet samples to be made by eliminating air but allowing water vapor into the sample chamber. However, -evaporation from and condensation on the sample may occur during the pumpdown sequence used to reach thisstate which means that the sample may not be in its natural state when viewed if due care is not taken. In thispaper, the pumping system of the ESEM is described mathematically and expressions derived for the evaporationand condensation. This treatment is then used to calculate the optimum pumpdown sequence. The importance ofusing the optimized procedure is illustrated with micrographs of fat emulsions.

303 R.E. Cameron, University of Cambridge, Dept. of Materials Science and Metallurgy, EnvironmentalSEM: Principles and Applications, Microscopy & Analysis , May 1994.

Key Words: Environmental Scanning Electron Microscope (ESEM)

Abstract: Conventional scanning electron microscopy (SEM) is firmly established as a standard analyticaltool. However, there have always been limitations on the samples which may be observed and the experimentswhich may be performed. Firstly, conducting coatings are needed on insulating samples to avoid build-up ofcharge and the consequent deterioration in image quality. This had rendered dynamic experiments on insulatorsdifficult, since any change in the sample damages the coating. Secondly, the high vacuum within microscope hasmeant the samples must not contain any volatile species. Samples which are normally hydrated, for example, mustbe dried or frozen before observation. The Environmental Scanning Electron Microscope (ESEM) overcomes boththese limitations. This article describes the principles behind the operation of the ESEM and discusses the newclasses of experiment now possible. Examples of the use of ESEM are taken from a range of scientific disciplines.

304 N. Baumgarten, Environmental SEM Premieres, Nature Vol., 341, No. 6237, pp. 81-82 7th September,1989 © Macmillian Magazines Ltd. 1989

Key Words: Environmental Scanning Electron Microscope (ESEM)

Abstract: The Environmental Scanning Electron Microscope (ESEM) eliminates the high vacuumrequirement of conventional SEM, allowing the analysis of unprepared, wet samples.

305 R. Mulvaney, E.W. Wolff, K. Oates, Sulfuric acid at grain boundaries in Antarctic ice. Nature Vol.331, No. 6153, pp. 247-249, 21 January 1988 © Macmillian Magazines ltd., 1988.

Key Words: Antarctic ice, Sulfuric acid

Abstract: It has been suggested that acids in the cold polar ice sheets may exist as aqueous mixtures atgrain boundaries. This assumption can correctly predict the d.c. conductivity of polar ice, but this does not provethe existence of acids or liquid veins at grain boundaries, and this remains controversial. In this study we used ascanning electron microscope (SEM) equipped with a cold stage and an energy-dispersive X-ray microanalysisfacility, to determine the location of sulfur in ice from the Antarctic Peninsula. As expected, sulfur wasundetectable in the bulk of the ice. However, at the junctions where three grains met (triple-junctions), sulfur wasfound in concentrations greater than 1M in areas of <1µm2. Calculations show that between 40 and 100% of thesulfuric acid present in this ice was found at the triple-junctions, and would have been liquid at ice-sheettemperatures. This finding, if general, has considerable implications for many of the physical properties of polarice.

306 Leon F. Keyser, Ming-Taun Leu, Surface Areas And Porosities Of Ices Used To SimulateStratospheric Clouds. Earth and Space Sciences Division Jet Propulsion Laboratory, California Instituteof Technology, Pasadena, CA 91109.

Key Words: ice



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Abstract: Low temperature ices formed by deposition from the vapor phase are used as laboratorysimulations of stratospheric ice clouds. To obtain intrinsic reactivities of these ices, detailed information on theirphysical structure is required. Surface areas, bulk densities and porosities are determined for H20 ice and HN03-H20 ices formed or annealed at temperatures from 85 to 265 K. Bulk densities and porosities are determinedphotogrammetrically. Scanning electron microscopy is used to obtain particle sizes and to study the morphology ofthe ices at several temperatures. Total surface areas are obtained from BET analysis of gas adsorption isotherms.Comparisons of the experimental isotherms with non-porous reference samples are used to determine the particleporosity due to micro and meso pores as well as the external area of the ice particles. Pore-size analysis yields theinternal surface area and an estimate of the particle porosity that agrees very well with the porosity obtained fromthe comparison plots. The sum of the internal and external areas is consistently lower than the BET area; this plusthe evidence for porosity obtained from the comparison plots indicates that part of the BET value is due to porefilling and, thus, cannot be considered a true surface area. External and internal surface areas as well as particleporosities are found to decrease sharply with temperature between 85 and 240 K, although bulk porosities changevery little. This suggests that the observed surface loss is due to pore closure, particle growth, and sintering.

307 Timothy J. Singler, James A. Clum, Dept. of Mechanical Engineering State University of New York atBinghamton, Edward Prack, Corporate Manufacturing Research Center, Motorola Inc., Schaumburg, IL60196, Microscopic Observations of Solder-Substrate Interactions.

Key Words: solder

Abstract: Preliminary results from solderability studies of Pb/Sn solder alloys wetting Au metallization arepresented. The focus of these studies is to elucidate the physiochemical aspects of solderability, in particular therelationship between liquid composition and wetting. Spreading front morphology is discussed and a possiblemechanism for observed rapid spreading sequences is advanced. A composition study of a spreading sequenceexhibiting a precursor film is presented along with a discussion of the role of the film in the overall wettingprocess.

308 H.S. Betrabet, J.K. McKinlay and S.B. McGee, Dynamic Observations of Sn-Pb Solder Reflow in aHotstage Environmental Scanning Electron Microscope, Philips Laboratories Briarcliff, © NorthAmerican Philips Corporation, 1991, Document No. MS 91-021

Key Words: Environmental SEM. hot-stage SEM, solders, microstructure, dispersion strengthening,microstructural refinement

Abstract: Solidification behavior of solders has a critical effect on the resulting microstructures and hencemechanical properties. Therefore, it is essential to understand the effects of soldering processing parameters onmicrostructure to engineer optimum microstructures. Microstructural changes in the solder that occur during thereflow process were studied in a hot-stage environmental scanning electron microscope (ESEM). An off-eutecticSn6O-Pb4O solder and a dispersion strengthened solder with the same Sn-Pb ratio were reflowed in an ESEM, andchanges in the microstructure were recorded on video tape. The dissolution and nucleation of grains duringmelting and solidification were observed. It was found that the microstructure of the conventional solder becamecoarser when it was allowed to solidify from a melt where the proeutectic lead was not completely dissolved. Grainrefinement was observed in dispersion strengthened solder where the dispersoids acted as heterogeneous nucleationsites.

309 John G. Sheehan, L.E. Scriven, Assessment of Environmental Scanning Electron Microscopy forCoating Research, Dept. of Chemical Engineering and Materials Science, University of Minnesota. 1991Coating Conference.

Key Words: Environmental Scanning Electron Microscope (ESEM), high pressure scanning electronmicroscopy, drying of paper, cryogenic scanning electron microscopy

Abstract: Environmental Scanning Electron Microscope (ESEM) is a new groundbreaking technique thatimages samples in a gaseous environment at pressures up to 2.7kpa (20 Torr). This paper reports an exploration of



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the capabilities of the ESEM for examining the wetting and drying of paper, and the drying of a coating formula.Breaking of fibers was seen during wetting and drying of 80# paper. But images must be interpreted with greatcare because electron beam radiation can damage wet cellulose fibers. In a coating formula dried in the ESEM,alignment of kaolin platelets was examined. This paper also assesses the potential for combining ESEM andcryogenic SEM for advantages of both.

310 P. Forsberg, P. Lepoutre, Degradation of Pulp Papers Under Electron Beam, University of Maine,Dept. of Chemical Engineering, Jenness Hall, Orono Maine 04469, Submitted to Nordic Pulp and PaperResearch Journal.

Key Words: Pulp, Kraft, Thermo-mechanical pulp, Lignin, Electron Microscopy, ESEM Degradation,Irradiation

Abstract: Experiments have been made to try to explain the striking difference in irradiation in thescanning electron microscope between kraft and TMP fibers. TMP fibers remain intact while kraft fibers degradequickly at high humidity, rendering them featureless. The water extractives and the benzone-toluene extractivesfrom TMP, abietic acid and finally lignin were added to kraft handsheets in order to determine which woodcomponent protects the carbohydrates in TMP. Only lignin gave protection against irrigation damage. The exactmechanisms of degradation, presumably caused by free radical reactions, of protection by lignin and of theaccelerating effect of water are not known. It appears that lignin protects cellulose when it is intermixed with it(secondary wall) as well as when it forms a sheath around it (middle lamella).

311 P. Forsberg, P. Lepoutre, A New Insight into the Fiber-rising Phenomena, University of Maine, Dept. ofChemical Engineering, Jenness Hall, Orono Maine 04469, Nordic Pulp and Paper Research Journal No.3/1992.

Key Words: fiber-rising, scanning electron microscopy

Abstract:

312 H.C. Greenblatt, M. Dombroski, W. Klishevich, J. Kirkpatrick, I. Bajwa, W. Garrison, B.K. Redding,Encapsulation and Controlled Release of Flavours and Fragrances, Royal Society of Chemistry, 1993V:138, pp. 148-1963

Key Words: flavours and fragrances

Abstract: Encapsulation and controlled release of flavours and fragrances has revolutionized the food andfragrance industries. Microencapsulation is a process in which small amounts of liquids, solids or gases are coatedwith materials which provide a barrier to undesirable environmental and/or chemical interactions (e.g., heat,moisture, oxidation) until release is desired. Conventional Microencapsulation techniques include spray-drying,liquid phase methods employing coacervation and in-situ polymerization. Typical advantages to encapsulatingfoods and fragrances are outlined.

313 Brendon J. Griffin, Rachael L. Trautman, Jeanette Coffey, X-ray Resolution at Low Chamber Pressuresand Chamber Gas Fluorescence in the ElectroScan ESEM. Center for Microscopy and Microanalysis,The University of Western Australia., Nedlands, W.A. Australia 6009.

Key Words:

Abstract:

314 C.E. Kalnas, J.F. Mansfield, G.S. Was, J.W. Jones, An in-situ bend fixture for deformation andfracture studies in the Environmental Scanning Electron Microscope., Materials Science andEngineering Department, University of Michigan, Ann arbor, MI 48109.

Key Words:



rev. 8

Abstract: A computer controlled loading fixture has been designed to allow in-situ observation of fractureprocesses during bending deformation of metal/ceramic microlaminates in an ElectroScan EnvironmentalScanning Electron Microscope (ESEM). The stage has the capability of accommodating either 3 or 4 pointbending experiments. A unique design feature of the stage is that the specimen surface remains at a fixed distancefrom the secondary electron detector and, hence, in focus during bending: the sample rests on the fulcrum whichremains in a fixed position while the restraints that grip the ends of the sample descend on a ball slide. The systemis controlled by an MacIntosh computer -Instruments NB-MIO-16L-9 data acquisition card. National InstrumentsLabVIEW82 software is used to control the stage displacement and to record the load cell and transducer outputs.The operation of this instrumentation in the ESEM is illustrated by the study of fracture processes in ceramic andceramic/metal microlaminate films deposited on ductile metallic substrates.

315 Po-Fu Huang, Barbara J. Turpin, Mike J Pipho, David B. Kittleson, Peter H. McMurry, Cloud Processingof Diesel Chain Agglomerates, for submission to Journal of Aerosol Science, Particle TechnologyLaboratory, University of Minnesota, Minneapolis, MN 55455 Publication Number 875, August 1993.

Key Words: cloud processing

Abstract: Diesel engines emit chain-agglomerate particles that can serve as cloud condensation nuclei.This research uses an Environmental Scanning Electron Microscope (ESEM) to study the effect of cloudprocessing on morphologies of individual diesel chain-agglomerates. Particles produced using a Caterpillar 3304diesel engine from fuels with sulfur contents of 0.84%, 0.32% and 0.034% by weight were collected on siliconwafer substrates. They were subjected to 1-3 water condensation - evaporation cycles in the ESEM. This processwas recorded on video tape, and digitized images of individual particles were used to find the particle's fractaldimension before and after each condensation - evaporation cycle.Significant collapse occurred in particles generated from both the mid-range sulfur fuel (0.32% S) and the lowsulfur fuel (0.034% S). The average fractal dimension of the particle images increased from 1.56 to 1.76 and from1.40 to 1.54 for particles from low and midrange sulfur fuel respectively. We observed no significantmorphological change in particles from high sulfur fuels. The experiments reflect lower limits for the degree ofcollapse that diesel chain-agglomerate particles undergo during atmospheric cloud processing.

316 Mehta, S. . Jones, R., Chatterji, J.. and McPherson, G. Effects of amorphous and crystalline silica onphase chemistry, microstructure and strength of set cement at elevated temperatures., ARCOExploration and Production Technology, Plano, Texas 75075, Halliburton Energy Services, Duncan,Oklahoma 73533

Key Words:Abstract: Strength retrogression of cement pastes cured at elevated temperature is a well-knownphenomenon. To offset this decrease in compressive strengths, 35 to 70% crystalline silica is added to cementslurries that are cured at or above I 110°C (230'F). Crystalline silica addition minimizes the conversion of C-S-Hgel to a-C2SH, which is thought to be the primary cause for strength retrogression at elevated temperatures.However, it has been also observed that if crystalline silica is replaced by amorphous silica such as silica fume, thebeneficial properties of silica additions may not be realized. The reason for this anomalous behavior of anomaloussilica is not well under-stood.

In this paper results of environmental scanning electron microscopy (ESEM), cryogenic scanning electronmicroscopy (Cryo-SEM) and x-ray diffraction (XRD) studies of high temperature, cured class H oil well cementpastes are presented in an attempt to delineate the effects of crystalline silica and amorphous silica additions onmicrostructure, phase chemistries and compressive strengths of pastes cured for one, three and seven days at I110°C (250'F). The results show that in one day cured samples there is a distinct difference in the hydrated phasespresent as well as in the nature of the matrix cohesiveness. These differences are reflected in the much highercompressive strength of the crystalline silica sample compared to the amorphous silica or neat samples. For 3 and7 days cured cements, however, the chemical differences tend to diminish, but the compressive strengths ofamorphous silica samples remain at or near that achieved after one day curing; whereas, for the crystalline silicasamples the strength increases by a factor of two after 7 days. 'These observations indicate that, for controlling



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strength retrogression at high temperatures, amorphous silica additions to cements should be avoided since theycan create major matrix defects and irregular gel chemistry with Ca/Si ratio that does appear to be suitable forconversion to a more stable tobermorite matrix.

317 Roger B. Bolon, Craig Robertson, X-RAY & MICROSTRUCTURAL E-SEM ANALYSIS OFREACTIONS AND NONCONDUCTING MATERIALS IN GASEOUS ENVIRONMENTS., GECorporate Research & Development, Schenectady, NY 12301

Key Words:Abstract: Biologists have long been interested in the ability to look at samples in their natural wet statewithout tedious sample altering preparations. This need led to the development of a new commercial instrumentand technique, capable of looking at samples in saturated water vapor as well as in a variety of other gases, calledenvironmental scanning electron microscopy (E-SEM). The key features of the instrument are an extensivedifferential pumping system between the chamber and column and a gas amplification secondary electron detector(GED). Together these developments provide new capabilities for looking at materials and performing dynamicexperiments not possible by traditional SEM techniques. This paper summarizes the key features which make theE-SEM different and presents a collection of experimental results from an ongoing feasibility study exploring newapplications for materials characterization.

318 D.A. Lange, Sujata, K., and H.M. Jennings, CHARACTERIZATION OF CEMENT-WATERSYSTEMS, Northwestern University, Evanston, IL

Key Words:

Abstract: Mechanical properties of cement and concrete are controlled largely by the microstructure whichdevelops during hydration. The major hydration product, calcium silicate hydrate (C-S-H), forms physical bondsbetween cement particles providing structural integrity to the bulk material.

Recent advances in electron microscopy, like the Environmental Scanning Electron Microscope (ESEM) from ElectroScanCorporation, have made possible direct observation of physical changes in hydrating cement. In the ESEM, the specimenchamber remains at pressures of 1-20 torr during imaging. Various gases and water vapor may be introduced into the chamber.A microinjector mechanism permits water to be added during imaging of the specimen. Dissolution and precipitation processesare observed uninterrupted and recorded on videotape.

New insights into cement hydration are emerging as a result of these new techniques. We have been able to watch themicrostructure change when individual cement particles dissolve and precipitation products form as water is added to drycement. Adjoining particles join to form bridges in the early stages of hydration, much as in the sintering process. C-S-H isfirst seen to form on the inside surfaces of pores and voids. The composition of the material is obtained from dot maps by anEnergy Dispersive X-ray analyzer coupled with an Image Analysis system.

Other ESEM projects in progress include studies of effects of drying of cured cement, effects of different cement mixingtechniques, and analysis of cement grout microstructures.

319 Hoyberg, K.; Knaggs, H., Environmental scanning electron microscopy of microcomedones -Proceedings - Annual Meeting, Microscopy Society of America 1994.. p 370-371 1994

Key Words: Electron Microscopy; Environmental

Abstract: Environmental Scanning Electron Microscopy (ESEM) allows the direct observation of wet, dry,and nonconductive specimens without sample preparation. Microcomedones extracted from cyanoacrylate biopsytechnique were examined via ESEM. ESEM provides a viable technique to monitor the surface of a substratebefore and after treatment to determine the efficacy of products. This technique will also be used to study theeffects of other known anti-acne agents as well as acne products. 3 Refs.

320 Forsberg, Paivi; Lepoutre, Pierre, ESEM estimation of the roughening of paper in high moistureenvironment -Proceedings of the International Printing and Graphic Arts Conference, 1994. TAPPIPress, Atlanta, GA, USA. p 229-236 1994Univ. of Maine, Orono, ME, USA Proceedings of the



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International Printing and Graphic Arts Conference - Halifax, Canada. Proceedings of the InternationalPrinting and Graphic Arts Conference

Key Words:

Abstract: Supercalendered filled (SC) and light weight coated (LWC) papers were examined using anenvironmental scanning electron microscope (ESEM). Large structural surface changes were observed duringcondensation of water on the surface in a high moisture environment. In the case of LWC papers, underlying fiberprotrude and appear extensively swollen. SC papers show significant roughening during wetting but there was noindication of ribbon-to-tube shape change of individual fibers.

321 Meredith, P., Donald, A.M., Luke, K. Pre-induction and induction hydration of tricalcium silicate: anenvironmental scanning electron microscopy study. Journal of Materials Science V30 N8 Apr. 15,1995. p 1921-1930

Key Words: electron microscopy, environmental

Abstract: Environmental Scanning Electron Microscope (ESEM) has been used to study the every earlypre-induction, and induction physical processes that occur in the hydration of tricalcium silicate. An in-situexperimental technique is described which allows direct, real time observation of the sub-micrometermorphological changes that take place during this reaction. The results of this investigation are correlated withkinetic data obtained by differential scanning calrimetry (DSC). In this way, microstructural evolution has beenidentified with the stages of very early hydration. Upon first contact with water. a gelatinous coating was seen toform at grain surfaces and a crystalline secondary product was observed at the end of an extensive dormant period.These findings are viewed in the light of previous “wet” and “dry” microscopy studies, and are discussed withinthe framework of ordinary Portland cement as a possible explanation of induction. Comment is made as to thesuitability of environmental SEM for analysis of such materials.

322 Belenii, I.; Ebrahimi, M.; Hascicek, Y. S. Study of thermal expansion of Bi-2212/Ag tape conductorsusing ESEM - INS Physica C (Netherlands) VOL. 247 NO. 3-4 1 June 1995 PP. 371-5 12 reference(s)ISSN- 0921-4534 CODENPHYCE6, - Nat. High Magnetic Field Lab., Tallahassee, FL, USACOPYRIGHT OF BIBLIOGRAPHIC- Copyright 1995, FIZ Karlsruhe

Key Words:

Abstract: Thermal expansion of Bi-2212 tapes dip coated on silver substrate was studied between roomtemperature and approximately 1000 K using an ElectroScan ESEM equipped with a hot stage. We showed thatthis can be a simple alternative technique when other conventional techniques have experimental difficultiesbecause of the sample geometry and size. Extensive shrinkage (more than 5%) was observed upon first heating ofthe green Bi-2212 which was removed from the silver substrate. The green composite tape more or less followedthe thermal expansion of silver tape on which it was coated. Thermal expansion of fully heat-treated Bi-2212/Agsuperconducting composite tape is similar to that of silver tape up to about 650 K. Between approximately 650 Kand approximately 1 000 K the composite exhibits less expansion.

323 Gergova, Katia; Eser, Semih; Schobert, Harold H.; Klimkiewicz, Maria ;Brown, Paul W. Environmentalscanning electron microscopy of activated carbon production from anthracite by one-step pyrolysis-activation - EIX 95-37 EIX95372798448 NDN- 017-0234-8363-9 Fuel v 74 n 7 Jul 1995. p 1042-10481995 Article ISSN-0016-2361 CODEN-FUELAC AUTHOR AFFILIATION-Pennsylvania State Univ, UniversityPark, PA, USA

Key Words:

Abstract: Experiments were carried out to produce activated carbons from anthracite using one-step steampyrolysis-activation. Environmental scanning electron microscopy (ESEM) was used to observe the porositydevelopment in real time. The anthracite samples were heated in different gas atmospheres before steamactivation. The ESEM observations showed that the activation agent had a significant effect on the porosity of



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activated carbon produced from anthracite. The activated carbon produced by steam activation at 850 degree C for6 h had the highest surface area and a well-developed porous structure. Substantial activation of anthracitesurfaces and formation of extensive porosity occurred under the same conditions but with steam at 270 Pa insteadof atmospheric pressure. Air treatment at 300 degree C for 3 h before steam activation also led to production ofactivated carbon with well-developed porosity. An important advantage of the activated anthracites produced inthis study is their microporous structure with a considerable fraction of pores of molecular dimensions. Thisindicates that molecular sieve materials can be produced from Pennsylvania anthracite by one-step pyrolysis-activation under appropriate conditions. (Author abstract) 20 Refs.

324 Albert Folch, Javier Tejada, Christopher H. Peters , Mark S. Wrighton, Electron beam deposition ofgold nanostructures in a reactive environment, 2080 Appl. Phys. Lett. 66 (16), 17 April 19950003-6951/95/66(16)/2080/3/$6.00 (D 1995 American Institute of Physics

Key Words:

Abstract: Electron beam deposition (EBD) is a maskless technique suitable for the fabrication ofmanometer scale structures. Metals can be deposited from an organometallic gas, but simultaneous carbondeposition typically yields grossly impure (-25% metal) deposits. We have found that the metal content of thedeposited solid is dramatically improved by performing the whole EBD process in a reactive gaseous environmentcontaining a source of oxygen (02, or H20) in addition to the organometallic gas. With simple procedures weprepared Au deposits showing significantly diminished C content (up to 50% metal) as the partial pressure Of 02

(or H20) is increased in the gas.

325 Abe, T., Ohmori, ., Nikaido, H., Kimura, H., Ozawa, M., Kinbara, ., 1992, Influence of ion beamirradiation on the structure and properties of dielectric thin films], Journal of the Vacuum Society ofJapan, 35, 9, 773-80

Key Words: Crystal atomic structure of inorganic compounds, Density of solids, Dielectric thin films, Ionbeam effects, Magnesium compounds, Refractive index, Scanning electron microscope examination of materials,Wetting, Zinc compounds, Ion beam irradiation, Structure, Dielectric thin films, Ion-beam-assisted deposition,Refractive indices, Ion beam power, Film density, Environmental scanning electron microscopy, Imperviousness,Water, Wetting property, MgF/sub 2/, ZnS films

326 Bower, N.W., Stulik, D.C., Doehne, E., D 1994, A critical evaluation of the Environmental ScanningElectron Microscope for the analysis of paint fragments in art conservation, J Fresenius J Anal Chem.,348, 5-6, 402-410, F .ih

Abstract: X Cross-sections from medieval paintings by Cenni di Francesco and Dosso Dossi were analyzedfor the inorganic components as well as the binding media using an environmental scanning electron microscope(E-SEM). the advantages of this instrument compared to a normal SEM-EDX are illustrated and a number ofoptimization studies are reported. It was found that using a chamber gas pressure of 1.5 kPa and a tungsten sourceinstead of the usual LaB6 source with the 38kPa pressure normally used for imaging would significantly improvethe x-ray analyses. Quantitative analyses for most of the commonmedieval pigments are also presented.

327 Chen, J., Brooks, K.G. Udayakumar, K.R., Cross, L.E., D 1991, Crystallization dynamics and rapidthermal processing of PZT thin films, J Ferroelectric Thin Films II Symposium, E Edited by: Kingon,A.I, E Edited by: Myers, E.R, E Edited by: Tuttle, B, I Mater. Res. Soc, C Boston, MA, USA, P 33-8, SFerroelectric Thin Films II Symposium



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Key Words: Crystallization, Ferroelectric thin films, Lead compounds, Rapid thermal processing, Scanningelectron microscope examination of materials, Rapid thermal processing, Crystallization process, EnvironmentalScanning Electron Microscopy, Ferroelectric thin films, X-ray diffraction, Microstructure, 10 1 s, 600 degC, 700degC, PZT thin films, PbZrO3TiO3, O 2-4 Dec. 1991

328 Danilatos, G.D., D 1990, Equations of charge distribution in the environmental scanning electronmicroscope (ESEM) J Scanning Microscopy V 4 N 4 P 799-823

Key Words: Electric charge, Electron probe analysis, Gas sensors, Scanning electron microscopy , Chargedistribution equation, Gas ionization, Gaseous detector, Environmental scanning electron microscope, ESEM,Charge density, Current flow, Electrode configuration, Electron probe, Electron skirt, Backscattered electrons

329 Danilatos, G.D., D 1990, Mechanisms of detection and imaging in the ESEM, Journal ofMicroscopym V 1, P 9-19,

Key Words: Scanning electron microscopes, Scanning electron microscopy, Secondary electrons, Imaging,Image formation, Charge carriers, Signal detection, Imaging insulators, Environmental scanning, electronmicroscope, Backscattered electrons

330 Doehne, E., Stulik, D.C., D 1990, Applications of the environmental scanning electron microscope toconservation science, Scanning Microscopy, V 4, N 2, P 275-86

Key Words: Environmental degradation, Scanning electron microscopy, Dead Sea scrolls, Environmentalscanning electron microscope, Conservation science, Research potential, Dynamic study, Wetting, Drying, Adobesamples, Semi-dynamic study, Exposure to formaldehyde, Electron imaging, Outgassing samples, Parchment,Swabs from Sistine Chapel cleaning, X-ray analysis, Uncoated insulators, Garnet jewelry, Deteriorationmechanisms, Material treatments, Ancient materials, Pb corrosion, Au jewelry,

331 Doehne, Eric Stulik, Dusan 1991, Dynamic studies of materials using the environmental scanningelectron microscope, Materials Research Society, 9800 McKnight Rd., Suite 327, Pittsburgh, P 31-38

KeyWords:

Abstract: Dynamic studies permit the observation of microscopical changes ofmaterials over time as various factors alter an object. Using this methodology, processes important in artconservation and archaeology such as the wetting and drying of consolidated and unconsolidatedbuilding materials or the corrosion of metals from air pollutants can be studied in situ and in tempora. thedevelopment of the environmental scanning electron microscope (E-SEM) has made it possible to videotape thesedynamic processes at nearly the same resolution limits as traditional SEM technologies without elaborate samplepreparation. Experiments examining salt crystallization, shrinkage in adobe, and lead corrosion illustrate the valueand applicability of the new E-SEM technology.*7 refs.

332 Doehne, E., Bower, N., D 1993Empirical evaluation of the electron skirt in the environmental SEM: Implications for energydispersive X-ray analysis, Microbeam Analysis, V 2, supplement, P S35-36



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333 Doehne, E.,Bower, N., D 1993, Experimental conditions for semi-quantitative SEM/EDS of painting,cross sections using the environmental scanning electron microscope, Microbeam Analysis, V 2,supplement, P S39-40

334 Doehne, E., D 1994, In situ dynamics of sodium sulfate hydration and dehydration in stone pores:Observations at high magnification using the environmental scanning electron microscope, IIIInternational Symposium on the Conservation of Monuments in the Mediterranean Basin, E Fassina, V. EOtt, H., E Zezza, F., Soprintendenza ai Beni Artistici e Storici di Venezia, C Venice, Italy, P 143-150, InEnglish

335 Farley, A.N., Shah, J.S., D 1990, Primary considerations for image enhancement in high-pressurescanning electron microscopy. 1. Electron beam scattering and contrast, Journal of Microscopy, V 3, P 379-88

Key Words: High-pressure techniques, Scanning electron microscopy, Elastic scattering cross sections. Imageenhancement, High-pressure scanning electron microscopy, Electron beam scattering, Resolution, Moist-environment ambient-temperature SEM, Inelastic scattering cross-sections, Energy range, Ionization efficiency,Water vapour, Image contrast, Step contrast function, . Beam voltage, . Beam scattering, 5 to 25 keV, N/sub 2/,

336 Fujimaki, N., Kano, Y., Ishikawa, H., Ohmori, A., Kawata, S., D 1990, Some Observations on Mouse-Tissues with the Environmental Scanning Electron-Microscope (ESEM), Journal of ElectronMicroscopy, V 39, N 4, P 299-299

337 Huang, Po-Fu, Turpin, B.J., Pipho, M.J., Kittelson, D.B., McMurry, P.H., 1994, Effects of watercondensation and evaporation on diesel chain-agglomerate morphology, Journal of Aerosol Science, V25, N 3, P 447-59

Key Words: Aerosols, Condensation, Evaporation, Fuel, Internal combustion engines, Organic compounds,Scanning electron microscopy, Water condensation, Water evaporation, Diesel chain-agglomerate morphology,Cloud condensation nuclei, Environment scanning electron microscope, Cloud processing, Morphologies,Caterpillar 3304 diesel engine, Fuels, Si wafer substrates, Water condensation-evaporation cycles, Video tape,Digitized images, Particle's fractal dimension, Atmospheric cloud processing, Diesel engines

338 Kawata, S., D 1991, [Environmental scanning electron microscope], Journal of the Japan Society ofPrecision Engineering, 57, N 7, 1178-81

Key Words: Scanning electron microscopes, Townsend discharge, Scanning electron microscope,Environmental scanning microscope, Environmental secondary electron detector, Oligo-scattering, Backscatteringelectrons, First Townsend coefficient, Environmental gas, Charge neutralization



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339 Kodaka, T., Debari, K., Sato, T., Tada, T., D 1991, The Environmental Scanning Electron-Microscope(ESEM) Observation of Human Dentin, Electron Microsc, 40 4, P 267-267, Journal Article

340 Kodaka, T., Toko, T., Debari, K., Hisamitsu, H., Ohmori, A., Kawata, S.D 1992, Application of the Environmental SEM in Human Dentin Bleached With HydrogenPeroxide Invitro, Journal of Electron Microscopy, V 41, N 5, P 381-386

Key Words: Microbiology/Cell Biology

341 Kozuka, Y., Nakamura, A., Futaesaku, Y., Inoue, S., D 1991, Dynamic Observations of ParticulatedSpecimens Under ESEM - a Model Experiment Using Cryptomeria-Japonica Pollen Grain, ElectronMicrosc., V 40, N 3, P 204-204

342 McDonough, C., Gomez, M.H., Lee, J.K., Waniska, R.D., Rooney, L.W., D 1993, Environmentalscanning electron microscopy evaluation of tortilla chip microstructure during deep-fat frying,Journal of Food Science, V 58, N 1, P 199-213

Key Words: Food Science/Nutrition,

Abstract: Changes that occur in the structure of corn tortilla chips during frying and the various aspects ofoil seepage into the baked chips were investigated. Chip samples were subjected to environmental scanningelectron microscopy ESEM. Starch content, the enzyme susceptible starch ratio, moisture content and oil contentwere calculated. the applicability and limitations of ESEM were demonstrated.

343 Rodriguez, M.A., Chen, Bin-Jiang,, Snyder, R.L., D 1992, The formation mechanism of texturedYB2Cu3O7-?, Physica C, 195, N 1-2, P 185-94

Key Words: Barium compounds, Chemical reactions, Crystal growth from solution, Crystal microstructure,Dissociation, Dissolving, High-temperature superconductors, Optical microscopy, Scanning electron microscopeexamination of materials, Texture, X-ray diffraction examination of materials, Yttrium compounds, Hightemperature superconductors, Post-mortem SEM analysis, Y source, Y deficient liquid phase, 211 dissolution,Formation mechanism, Liquid phase, Peritectic reaction, Y/sub 2/BaCuO/sub 5/ (211) , Real-time analysistechniques, High-temperature X-ray diffraction, High-temperature optical microscopy, Environmental scanningelectron microscopy, Microstructural development, 123 formation, Peritectic melt, Crystalline 211, TexturedYBa/sub 2/Cu/sub 3/O/sub 7- delta /

344 Sarkar, S.L., Xu,.M. D 1992, Preliminary Study of Very Early Hydration of Superplasticized C3A+,Gypsum by Environmental SEM, Cement and Concrete Research, V 22N 4, P 605-608, F .ih

Key Words: Materials-ENGI



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345 Sayer, M., Nolan, P., Hansson, C.M., D 1993, Scanning Electron Microscopy Without Pain - theEnvironmental SEM, Canadian Ceramics Quarterly-Journal of the Canadian Ceramic Society, V 62, N2, P 104-105Reprint: QUEENS UNIV,DEPT MAT & MET ENGN KINGSTON K7L 3N6, ONTARIO CANADA

346 Stulik, Dusan, Doehne, Eric, D 1991, Applications of environmental scanning electron microscopy inart conservation and archaeology, Materials Research Society, 9800 McKnight Rd., Suite 327,Pittsburgh, V 185, P 23-30,

Abstract: 2 the principles of environmental scanning electron microscopy (E-SEM) are explained anddiscussed. the performance of the E-SEM compares favorably with the performance of traditional SEMinstruments. This new technology has significant advantages in art conservation and archaeology. the authorsdescribe several pilot studies which explored potential uses of the E-SEM. Electron micrographs recorded frommoist, outgassing, and difficult to coat samples are presented, together with x-ray spectra recorded fromuncoated samples of electrically nonconductive materials. -- AATA*Includes 5 bibliog. refs.

347 Thaveeprungsriporn, V., Mansfield, J.F., Was, G.S., D 1994Development of an economical electron backscattering diffraction system for an environmental scanningelectron microscope, Journal of Materials Research, V 9, N 7, P 1887-94

Key Words: Backscatter, Electron diffraction examination of materials, Scanning electron microscopes,Economical electron backscattering diffraction system, Environmental scanning electron microscope, Phosphorcoated screen, Microscope environment, Image, Electron backscattering diffraction patterns, CCD TV camera,Leaded glass port, Microscope specimen chamber, Spatial resolution, Grain boundary misorientation, Ni-Cr-Fealloy, Selected area channeling patterns, On-line analysis, Grain boundary character distribution,Thermomechanical treatment, Ni-Cr-Fe

Dept. of Nucl. Eng., Michigan Univ., Ann Arbor, MI, USA, July 1994, vol.9, no.7348 Wight, S.A., Zeissler, C.J., D 1993, Environmental Scanning Electron Microscope ImagingExamples Related to Particle Analysis, Microscopy Research and Technique, V 25, N 5-6, P 393-397

Key Words: Microbiology/Cell Biology; Instrumentation/Measurement

Reprint: NATL. INST. STAND & TECHNOL. BLDG. 222,RM A113 GAITHERSBURG, MD USA 208995-6349 Yamaguchi, T., Yanao, Y., D 1990, Environmental Scanning Electron-Microscope, Journal ofElectron Microscopy, V 39, N 4, P 284-284

350 Yamaguchi, T., Kawata, S., Suzuki, S., Sato, T., A Sato, Yu, D 1993, New linewidth measurementsystem using environmental scanning electron microscope technology, 6th International MicroProcess



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Conference, C Hiroshima, Japan, P 6277-80, S Japanese Journal of Applied Physics, Part 1 (RegularPapers & Short Notes)

Key Words: Scanning electron microscopy, Semiconductor technology, Spatial variables measurement,Linewidth measurement system, Environmental scanning, Electron microscope technology, Deep submicron devicemetrology tool, Hole observation

____________________________________________________________________________________________

351 Cameron, R. E., Donald, A. M., Journal of Microscopy, March 1994, Minimizing sampleevaporation in the environmental scanning electron microscope, P 227-237.

Keywords: Environmental scanning electron microscopy, ESEM, evaporation, condensation, pumpdownprocedure.Summary: The ElectroScan environmental scanning electron microscope (ESEM) enables wet samples to beobserved by eliminating air but allowing water vapour into the sample chamber. However, evaporation from, andcondensation on, the sample may occur during the pumpdown sequence used to reach this state, which means thatthe sample may not be in its natural state when viewed if due care is not take. In this paper, the pumping system ofthe ESEM is described mathematically and expressions are derived for the evaporation and condensation. Thistreatment is then used to calculate the optimum pumpdown sequence. The importance of using the optimizedprocedure is illustrated by micrographs of fat emulsions.

352 Danilatos, G. D., XII International Congress for Electron Microscopy, D 1990, P. 372-373, Detectionby Induction in the Environmental SEM.

Abstract: The advent of environmental SEM (ESEM) has revealed the true mechanism of detection, whenthe current mode is used. The ESEM allows the introduction of gas in the specimen chamber with a pressure atleast sufficient to maintain specimens in their wet state. The gas is also used to suppress charge accumulation oninsulating specimens and, furthermore, it can be used as a detection and amplification medium. The resolvingpower of the instrument is not impaired by the presence of gas, whereas new contrast mechanisms are nowpossible. The foundations of this technology have been outlined in a extended survey previous.

353 Danilatos, G.D., Journal of Microscopy, Mechanisms of detection and imaging in the ESEM, V 160,October 1990, P 9-19.

Keywords: Environmental SEM, ESEM, gaseous detector device, ionization and proportional counters,signal induction, insulators in ESEM.

Summary: For proper understanding of image formation using charge carriers, it is shown that signaldetection by means of induction must be considered. This explains the possibility of imaging insulators as well asother phenomena especially in the conditions of the environmental scanning electron microscope. In addition, abasic principle and method to separate the secondary and backscattered electrons is demonstrated.

354 Mehta, S., Jones, R., Caveny, B., Chatterji, J. McPherson, G. Environmental Scanning Electron Microscope (ESEM) examination of Individually hydrated Portland cement phases.

Abstract: The ability to examine in situ hydration as well as wet-hydrated products of Portland cement inthe ESEM offers new opportunities to characterize early cement hydration reactions. Furthermore, these reactionscan be better understood if pure cement components are hydrated separately in the ESEM without complexitiesintroduced form simultaneous hydration of other phases. In the present study we have characterized morphologyand phase chemistry of 1 to 150 hours--hydrated products of four separate cement components, C3S, C2S, C4AFand C3A. The results show unique hydrations characteristics associated with each of the four phases, which in turn



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may be used to isolate competing reactions during early hydration of these four phases in clinker thin sections anddetermine the role of lignosulfonate in retarding cement gellation.

355 Harner, A.L., Copeland, C.H., Grim, B.G., Destruction of Concrete By Fertilizers-Urea AmmoniumNitrate vs Concrete, National Fertilizer and Environmental Research Center, Tennessee ValleyAuthority, Muscle Shoals, Alabama

Abstract: As part of a research project on protection of concrete against agrochemicals, studies have beenmade of concrete deterioration using optical microscopy and an environmental scanning electron microscope,(ESEM), Urea ammonium nitrate is a widely used fertilizer material. Aqueous urea ammonium nitrate solutionsattack concrete by reaction with calcium hydroxide and weakening of the concrete matrix structure. Rinsing andair drying the surface of the concrete do not prevent further deterioration. Destruction continues with migration ofsubsurface components. The concrete is eventually reduced to aggregate and powder. Growth of water-soluble Ca(NO3)2. 4CO(NH2)2 has been observed on the surface of the concrete in these studies. This finding has implicationson the cleanup techniques required for spills. It also raises questions about the use of urea as a deicer near concretestructures with high nitrate concentrations in groundwater or from acid rain.

356 Caveny, B., McPherson, G., Brothers, L., Mehta, S., Crystal Phases of Cement Paste Cured in HighTemperature--CO2 Environment.

Abstract: Completion of geothermal wells in hostile environments require laboratory studies to determinewhich cement blends might work best for a given set of conditions. This paper details some data obtained fromblends that were cured in CO2 environments at 316° C. XRDA, ESEM, and light microscopy and other methodswere used in the analysis.

357 Miller, P.T., Farrington, S.A., Kovach, L., Petrographic Thin Section and Scanning ElectronMicroscope Analysis of a Mortar Fabricated in a Microgravity Environment: Preliminary Studies.

Abstract: A Portland cement mortar was mixed on board a recent space shuttle mission to study the effects of amicrogravity environment on the production of a hardened mortar. A control sample was subsequently prepared inthe same mixer under gravity conditions on the earth’s surface. The purpose of the study is the examination of thecement paste microstructure to determine the effects of microgravity on its development. Optical microscopy ofthin sections of mortar and scanning electron microscopy of fracture surfaces of mortar were chosen for theanalysis. Thin-section analysis suggested that the extent of aggregation of the calcium hydroxide crystals was lessunder the influence of microgravity. Scanning electron microscopy suggested that the microgravity allowed for theformation of a microstructure with a much more distinct void structure.



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358 Mehta, S., Jones, R. Chatterji, J. McPherson, G., Effects of amorphous and crystalline silica onphase chemistry, microstructure and strength of set cement at elevated temperatures.

Abstract: Strength retrogression of cement pastes cured a elevated temperature is a well knownphenomenon. To offset this decrease in compressive strengths, 35 to 70% crystalline silica is added to cementslurries that are cured at of above 110° C (230° F). Crystalline silica addition minimizes the conversion of C-S-Hgel to � -C2SH, which is thought to be the primary cause for strength retrogression at elevated temperatures.However, it has been also observed that if crystalline silica is replaced by amorphous silica such as fume, thebeneficial properties of silica additions may not be realized. The reason for this anomalous behavior of amorphoussilica is not well understood.

359 Peiming, W., Pingjiang, L. Zhiyuan, C., Research on the morphology of cement hydrates by SEM.

Keywords: hydrate, morphology, hydration space, environmental pressure

Abstract: This paper throws light on the morphology change of cement hydration products under theobservation of SEM. The results show that the morphologies are changed, some even significantly, with thesample grown within different free space, or under the observation of different vacuum degree and others.

360 Damidot, D., Sorrentino, F., Observation of the hydration of cement paste by ESEM: Care neededto study the early hydration, St. Quentin, Fallavier Cedex, France.

Abstract: Environmental scanning microscope (ESEM) is more and more commonly used to study thehydration of cement paste as wet samples can be directly observed. However in order to improve the observationconditions, one may be tempted partially or completely the water. Water removal from concentrated solutions caninduce very rapid precipitation of solids and thus conducts to false interpretations. This phenomena which isexpected to be all the more important during early hydration of cement paste as the aqueous phase is stronglysupersaturated with respect to some hydrates. In order to demonstrate this mechanism, supersaturated solutionsobtained during CA and C3S hydration have been evaporated in the ESEM chamber. Some solids are precipitatedas fine film or small crystals depending on the conditions. Especially portlandite can form small crystals when thesolution is supersaturated with respect to it. On the other hand, very rapid systems such as mixture of C3A andgypsum are less sensible because the hydrate precipitation (ettringite in this case) occurs practicallyinstantaneously. Thus care has to be taken when studying the early hydration of cement by ESEM in order toavoid an user-induced precipitation of hydrates.

361 Danilatos, G.D., Postle, R., The Time Temperature Dependence of the Complex Modulus of KeratinFibers, Journal of Applied Polymer Science, V. 28, P. 1221-1234, D. 1983.

Abstract: A fiber viscoelastometer 1,2 has been used by the present authors for the study of the dynamicmechanical properties of keratin fibers. These studies have been performed on fibers during extension, 3,4 orduring water sorption. 5,7 This previous work was performed at a constant temperature and frequency whereas theaim of the present paper is to examine the dynamic mechanical behavior of keratin fibers when the temperature orfrequency of oscillation is varied. A comparative presentation of other closely related work is necessary in order toevaluate the results obtained in the present work.

362 Danilatos, G.D., Postle, R., Dynamic Mechanical Properties of Keratin Fibers During Water Absorptionand Desorption, Journal of Applied Polymer Science, V. 26, P. 193-200, D. 1981.



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Abstract: The dynamic modulus and loss angle of keratin fibers have been measured during changes ofrelative humidity at a fixed fiber strain, temperature, and frequency of oscillation. From these measurements andthe observation of an overshoot in loss angle in particular, certain conclusions about the structure can be made.This overshoot during absorption can be attributed to an interaction between two phases of keratin fibers. When afiber at a fixed strain is dried from the wet state, the amount of � helices that have opened up during extension inwater remains practically constant. A fiber that has been extended in the dry state contains � helices which openmore rapidly than in the wet state for a given strain and rate of strain. When a wet fiber is dried and then rewettedwhile it is held at a fixed strain, the fiber achieves essentially the same structural state as in its original strainedstate.

363 Danilatos, G.D., Postle, R., Low Strain Dynamic Mechanical Properties of Keratin Fibers DuringWater Absorption, J. Macromol. Sci. Phys., B 19 (1) P. 153-165 (1981).

Abstract: Important phenomena during water absorption by keratin fibers have been observed by variousworkers. In this paper, the dynamic mechanical properties of keratin fibers at a constant frequency andtemperature have been studied during absorption while the fibers are held at a fixed low strain (< 1%). Acharacteristic overshoot in the loss angle during absorption has been observed, and an explanation in terms of theinteraction between two phases in keratin fibers is presented

364 Doehne, E., Stulik, D.C., Applications of the Environmental Scanning Electron Microscope toConservation Science, Scanning Microscopy, V. 4, N. 2, D. 1990, P. 275-286.

Abstract: The environmental scanning electron microscope (ESEM) provides electron imaging at relativelyhigh sample pressure, with imaging and analysis capabilities comparable to those of traditional high vacuum SEM.Several case studies demonstrate the advantages and research potential of this new technology as applied toconservation science: 1) dynamic study of wetting and drying of consolidated and unconsolidated adobe samples:2) semi-dynamic study of lead corrosion as a result of exposure to formaldehyde: 3) electron imaging of outgassingsamples-parchment: 4) study of uncoated, non-conductive samples-swabs from Sistine Chapel cleaning: 5) X-rayanalysis of uncoated insulators-gold and garnet jewelry. The environmental scanning electron microscope offersunique capabilities for dynamic experiments, imaging of outgassing samples and insulators which may be appliedto the study of deterioration mechanisms, material treatments, and ancient materials and technologies.

365 Bergstrom, T.B., Jennings, H.M., The Formation of Bonds in Tricalcium Silicate Pastes as Observedby Scanning Electron Microscopy, Journal of Materials Science Letters II, D. 1992, P. 1620-1622.

Abstract: Portland cement reacts with water to form a paste that is used extensively as the binder inconcrete. The reactions are extremely complex (1) and the developing microstructure is sensitive to the moisturecontent. The most abundant and important component of Portland cement is tricalcium silicate (C3S; throughoutthis letter cement chemistry notation is used: C=CaO, S= SiO2 and H=H2O), a mineral which is often studiedseparately in order to understand how it behaves in the more complex system.

366 Meredith, P., Donald, A.M., Luke, K., Pre-Induction and Induction Hydration of TricalciumSilicate: An Environmental Scanning Electron Microscopy Study, Cavendish Laboratory,Cambridge, University Physics

Summary: Environmental scanning electron microscopy (ESEM) has been used to study the very early pre-induction, and induction physical processes that occur in the hydration of tricalcium silicate. An in-situexperimental technique is described which allows direct, real-time observation of the sub-micron morphological



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changes that take place during this reaction. The results of this investigation are correlated with kinetic dataobtained by differential scanning calorimetry (DSC). Upon first contact with water, a gelatinous coating was seento form at grain surfaces and a crystalline secondary product was observed at the end of an extensive dormantperiod. These crystalline secondary product was observed at the end of an extensive dormant period. Thesefindings are viewed in the light of previous “wet” and “dry” microscopy studies, and are discussed within theframework of ordinary Portland cement as a possible explanation of induction. Comment is made as to thesuitability of environmental SEM for analysis of such materials.

367 Sujata, K., Jennings, H.M., Formation of a Protective Layer During the Hydration of Cement, Journalof American Ceramics Society, D. 1992, M. 196122.

Keywords: cements, hydration, protection, layers, electron microscopy.

Abstract: The mechanism for the slow rate of reaction between Portland cement and water during the earlystage is not well understood, but it probably is controlled by either the rate that the reactants defuse through abarrier that surrounds the unreacted cement grains or by the rate that nuclei of the stable product form and grow orby both rates. New evidence using environmental scanning electron microscopy is presented about the structure ofa layer that forms around the particles of cement. Preliminary observations that relate mixing to the structure ofthe layer are also presented

368 Lange, D.A., Sujata, K., Jennings, H.M., Observations of Wet Cement Using Electron Microscopy,Ultramicroscopy, V. 37, D. 1991. P. 234-238.

Abstract: Advances in scanning electron microscopy have made possible observations of wet cementspecimens at high magnifications. New techniques using the environmental scanning electron microscope allowthe study of cement-based materials at critical early stages of the hydration process with no disturbance to thematerial and its developing microstructure. The microscope provides specimen chamber pressures sufficientlyhigh for water to remain on surfaces and in the pore structure. A cooling stage facilitates observation of wetspecimens by lowering the temperature of the specimen and therefore the partial pressure necessary for liquidwater. A microinjector mechanism permits water to be added during imaging of the specimen. Dissolution andprecipitation processes in cement paste are observed uninterrupted and recorded on videotape. The advancedcapabilities have contributed new insight into microstructural development in cement past.

369 Derbin, G.M., Palsson, B.O., Mansfield, J.F., Wheatley, T.A., Dressman, J.B., Release Behavior fromEthylcellulose-Coated Pellets: Thermomechanical and Electron Microbeam Studies, PharmaceuticalTechnology, D. 1996, P. 70-81.

Abstract: Previous studies have shown that the release of drugs from pellets coated with ehtylcellulosepseudolatexes can, under certain formulation and coating conditions, vary with time of storage and the pH of therelease medium. In this work, X-ray energy dispersive spectroscopy (XEDS) was used to elucidate differences inthe surface composition, and environmental scanning electron microscopy (ESEM) was used to characterize thesurface morphology of ethylcellulose pseudolatex films formed on phenylpropanolamine hydrochloride pelletsunder different manufacturing conditions. Thermomechanical analysis (TMA) studies were also performed tocharacterize the thermal behavior of films cast from plasticized ethylcellulose-pseudolatexes. All findings wereconsistent with the hyothesis that heating and ethylcellulose pseudolatex film above its glass transition temperaturefacilittes film relaxation, resulting in drug release profiles that are virtually independent of storage under usualconditions and also independent of the pH of the release medium.

370 Carpenter, D.T., Smith, D.A., Lloyd, J.R., Observation of Passivated A1-1% Cu Lines UsingEnvironmental Scanning Electron Microscopy (ESEM), Department of Materials Science andEngineering, Lehigh University, Bethlehem, PA 18018.



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Abstract: Characerization of failure phenomena in passivated interconnects requires the ability ro observedynamic changes in buried lines (e.g. formation of electromigration voids or microstructural changes during ananneal). Conventional SEM cannot image passivated structures due to surface charging. HVSEM has been usedwith some success to image voids in metal lines under passivation, but it requires intensive specimen preparationand is not commercially available. 1,2 The present study is intended to determine whether ESEM is suitable forsuch dynamic experiments on passivated structures.

371 Roberts, R.A., Shukla, A.J., Rice, T., Characterization of Polyox® Granules using EnvironmentalScanning Electron Microscopy, Dept. of Pharmaceutical Sciences, College of Pharmacy, University ofTennessee, Memphis, TN 38163, Philips ElectroScan, Wilmington, MA 01887.

Keywords: environmental scanning electron microscope, ESEM, hydrophilic polymer, pharmaceuticalapplication, Polyox®, granulation

Summary: The Scanning Electron Microscope (SEM) has been frequently used in the pharmaceuticalindustry for studying pharmaceutical products. However, the technique does not allow for the continuouscharacterization of a product in both dry and hydrated states without processing the product. Through the recentadvent of the environmental scanning electron microscope (ESEM), it is now possible to observe a sample in boththe dry and hydrated states without extensive product preparation. The ESEM also allows for continualobservation during the hydration process from the dry state until the sample is dissolved. In this study,, the ESEMwas used to characterize the morphological differences and hydration patterns of granules formulated with a water-soluble hydrophilic swelling polymer, Polyox®. Two molecular weights (1,000,000 and 7,000,000) of the polymerwere used in concentrations ranging from 10% to 25% w/w. Visual differences in granule surface morphology anddifferences in hydration patterns were seen in granules prepared from different polymer concentrations. Themorphological data was corroborated by surface area measurements taken on a Micromeritics surface areaanalyzer. The rate at which the granule dissolved in the ESEM also correlated to the drug dissolution timesdetermined by the standard USP dissolution method.

372 Pesenti, F., Hassler, J.C., Lepoutre, P., Influence of Pigment Morphology on Microstructure and Gloss of Model Coatings, Paper Surface Science Program, Dept. of Chemical Engineering,

University of Maine,

Abstract: The gloss and surface microstructure of coatings made from pigments of different shapes areinvestigated. A theoretical TAPPI glos-roughness relationship gave a very good fit for all but clay. All pigmentswhose shape factor was close to one followed the same TAPPI gloss-ESD curve which was predicted from theexperimental roughness-ESD data. A preferential orientation of PCC needles in the coating application directionleads to a lower reoughness and a higher gloss in the direction.

373 Stanislawska, A., Lepoutre, P., Consolidation of Pigmented Coatings: Development of Porous Structure, Tappi Journal, V. 79, N. 5.

Abstract: The consolidation of pigmented coatings based on clay or ground calccium carbonate and latexwas examined by quenching the wet coatings at various stages of drying in liquid nitrogen and freeze drying (F-D).From scanning electron microscopy (SEM) examination of the F-D coatings and measurements of gloss, voidfraction, surface area, and light scattering, the process of porous structure development was followed. Pigmentshape affected the consoldiation process. Gloss of the consolidation process. Gloss of the allclay structures wasalways much higher than that of rhombic CaCO3. Pore sizes at al lconsolidation stages were smaller with clay thanwith CaCO3. Intense drying increased the shrinkage of all coatings, but thermal post-treatment of roomtemperatures-dried coatings had no effect on dimensions. Consolidation of coatings applied on paper wasexamined. The same increase in the gloss of F-D coatings up to the first critical concentration followed by a



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decline was observed. However, initial gloss values on paper and on plastic film were quite lower than that ofplastic coatings applied at low speed. this observation was unexpected and is significant. At the later stages ofconsolidation, the structure of the paper and plastic film coatings differed increasingly, as expected.

374 Shaler, S.M., Groom, L., Mott, L., Microscopic Analysis of Wood Fibers using ESEM and Confocal Microscopy, Wood Science and Technology, University of Maine, Oroni, ME, Southerin

Forest Expt. Sta., USDA Forest Service, Pineville, LA, Dept. of Forest Management,University of Maine, Orono, ME.

Abstract: Improvements in the properties of woodfiberplastic composites requires an understanding of themicrostrucure of the material, how it is impacted by processing, and the relationship to gross properties. Tworecently developed microscopic techniques permit determination of microstructural information unobtainable bytraditional scanning and light microscopy. Environmental scanning electron microscopy (ESEM) is similar totraditional electron microscopy but has improvements that allow imaging of specimens at a low vacuum (1-20torr). This feature permits water in either vapor of liquid form to remain in the specimens (under saturated vaporconditions). As a result, no speciment coating or dehydration is necessary. A single fiber mechanical tensiletesting assembly has been developed, which permits concurrent images and loads of individual wood fibers to beobtained while in the ESEM sample chamber. The impact of fiber morphology and processing-induced defects onfracture mode and mechanical properties have been determined for several fiber types. Additionally, the use ofdigital images from ESEM permits whole field displacement measurements of the fiber to be obtained through theuse of digital image correlation routines. The confocal laser scanning microscope is a device capable ofdeterminging the three demensional structure of a material by obtaining successive images (of very low field depthfocal planes) of the material cross section. This permits determination of fiber cross-sectional area and internalvoid structure within a composite or individual fibers (e.g., pit chamber). This information, in conjuction withESEM, permits new levels of detail in understanding fiber and composite microstructure and performance.

375 Mott, L, Shaler, S.M., Groom, L.H., A Technique to Measure Strain Distributions in Single WoodPulp Fibers, Wood and Fiber Science, 28 (4) 1996, P. 429-437.

Keywords: Fibers, micromechanics, strain, digital image correlation, tensile testing, environmental scanningmicroscopy.

Abstract: Environmental Scanning Electron Microscopy (ESEM) and digital image correlation (DIC) wereused to measure microstrain distributions on the surface of wood pulp fibers. A loading stage incorporating a fibergripping system was designed and built by the authors. Fitted to the tensile substage of an ESEM or PolymerLaboratories MINIMAT tester, it provided a reliable fiber straining mechanism. Black spruce latewood fibers(Picea mariana (Mill) B.S.P.) of a near zero microfibril angle displayed a characteristically linear load elongationform. ESEM was able to provide real-time, high magnification images of straining fibers, crack growth, andcomplex single fiber failure mechanisms. Digital images of single fibers were also captured and used forsubsequent DIC-based strain analysis. Surface displacement and strain maps revealed nonuniform straindistributions in seemingly defect-free fiber regions. Applied tensile displacements resulted in a strain bandphenomenon. Peak strain (concentration) values within the bands ranged from 0.9% to 8.8%. It is hypothesizedthat this common pattern is due to a combination of factors including the action of microcompressive defects andstraining of amorphous cell-wall polymeric components. Strain concentrations also corresponded well to locationsof obvious strain risers such as visible cell-wall defects. Results suggest that the ESEM-based DIC system is auseful and accurate method to assess and, for the first time, measure fiber micromechanical properties.

376 Dickson, R.J., LePoutre, P., Macro-and Micro-Mechanical Interlocking in Coating-Paper/Board Adhesion.



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Abstract: Adhesion between two surfaces involves physico-chemical interactions (acid-base and Lifshitz-van der Waals forces) and possibly mechanical interlocking (MI) if the substrate is porous and rough. Paper has aroughness and a network of pores. It could be expected that, when paper is coated the adhesion would containmechanical interlocking in addition to the physico-chemical interactions. Experiments were designed to measurethe level of mechanical interlocking by pretreating handsheets with a fluorocarbon, to remove the physico-chemicalinterations. Adhesion was measured through a peel test and a z-direction test. This work indicatied that as thesurface roughness increases then MI increases by providing sites for MI; coat weight non-uniformity influences thefailure mechanism so that the peel force, and the z-direction strength, appear to decrease with increasing coatweight. In some cases the peel force measured on coated-paper represented up to 60% of the delamination energyof the paper. From measurements of single fiber-coating adhesion it is concluded that the fiber’s micro-roughnesscan contribute up to 20% of the fiber-coating adhesion. In all casess where MI occurred either on a micro- ormacroscopic scale, in the interlocked areas the coating failed, thus making MI dependent on coating cohesion

377 Wight, Scott; Gillen, Greg and Herne, Tonya (1997) “Development of Environmental ScanningElectron Microscopy Electron Beam Profile Imaging with Self-Assembled Monolayers andSecondary Ion Mass Spectroscopy”, Scanning 19, 71-74.

Keywords: environmental scanning electron microscope; self-assembled monolayer; Monte Carlo; SAM;ESEM; backscatter

Summary: A method for demonstrating the scattering of the primary electron beam in the presence of a gashas been developed. A self-assembled decanethiol monolayer is damaged by primary beam electrons. Thedamaged portion of the monolayer is exchanged with another thiol-containing molecule by immersion in solution.The resulting film is imaged using a secondary ion mass spectrometer. Three-dimensional reconstruction of thedata yields a representation of scattered electrons in the gaseous environment of the environmental scanningelectron microscope.

378 Doehne, Eric (1997) “A New Correction Method for high-Resolution Energy-Dispersive X-RayAnalyses in the Environmeental Scanning Electron Microscope”, Scanning 19, 75-78.

Keywords: environmental scanning electron microscope; x-ray analysis; electron skirt; correction method

Summary: Spurious x-ray signals, which previously prevented high-resolution energy dispersive x-rayanalysis (EDS) in the environmental scanning electron microscope (ESEM), can be corrected using a simplemethod presented here. As the primary electron beam travels through the gas in the ESEM chamber, a significantfraction of the primary electrons is scattered during collisions with gas molecules. These scattered electrons form abroad skirt that surrounds the primary electron beam as it impacts the sample. The correction method assumes thatchanges in the width of the electron skirt with pressure are less important than changes in the skirt intensity; thismethod works as follows: The influence of the gas on the overall x-ray data is determined by acquiring EDSspectra at two pressures. Subtracting the two spectra provides us with a different spectrum which is then used tocorrect the original data, using extrapolation, back to the x-ray spectrum expected under high-vacuum conditions.Low-noise data are required to resolve small spectral peaks; however, the principle should apply equally to x-raymaps and even to low- magnification images.

379 Schnarr, Holger and Füting, Manfred W. (1997) “Some Aspects of Optimizing Contrasts for theInvestigation of Joint Materials in the Environmental Scanning Electron Microscope”, Scanning 19,79-84.

Keywords: environmental scanning electron microscopy; contrast phenomena; joint materials

Summary: In the environmental scanning electron microscope, material joints of different atomic mass anddifferent electrical conducting properties can easily be observed simultaneously without coating the specimen. Forsuch heterogeneous materials, the quality of the image can be optimized with respect to contrast and resolution ifthe contrast types as well as their significance to the composition of the image are known.



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380 Carlton, Robert A. (1997) “The Effect of Some Instrument Operating Conditions on the X-RayMicroanalysis of Particles in the Environmental Scanning Electron Microscope”, Scanning 19, 85-91.

Keywords: environmental scanning electron microscopy; x-ray microanalysis; beam broadening; energydispersive x-ray spectroscopy

Summary: The objective of this investigation was to evaluate the practical effects of electron beambroadening in the environmental scanning electron microscope (ESEM) on particle x-ray microanalysis and todetermine some of the optimum operating conditions for this type of analysis. Four sets of experiments wereconducted using a Faraday cage and particles of copper, glass, cassiterite and rutile. The accelerating voltage andchamber pressure varied from 20 to 10kV and from 665-66 Pa (5.0 to 0.5 torr), respectively. The standard gaseoussecondary electron detectors (GSED) and the long environmental secondary detectors (ESD) for the ESEM wereevaluated at different working distances. The effect of these parameters on the presence of artifact peaks wasevaluated. The particles were mounted on carbon tape on an aluminum specimen mount and were analyzedindividually and as a mixture. Substrate peaks were present in almost all of the spectra. The presence ofneighboring particle peaks and the number of counts in these depended upon the operating conditions. In general,few of these peaks were observed with the long ESD detector at 19mm working distance and at low chamberpressures. More peaks and counts were observed with a deviation from these conditions. The most neighboringpeaks and counts were obtained with the GSED detector at 21.5mm working distance, 10kV accelerating voltage,and 665Pa (5.0 torr) chamber pressure. The results of these experiments support the idea that the optimuminstrumental operating conditions for EDS analysis in the ESEM occur by minimizing the gas path length and thechamber water vapor pressure, and by maximizing the accelerating voltage. The results suggest that the analystcan expect x-ray counts from the mounting materials. These tests strongly support the recommendation of themanufacturer to use the long ESD detector and a 19mm working distance for EDS analysis. The results of theseexperiments indicate that neighboring particles millimeters from the target may contribute x-ray counts to thespectrum.

381 Jenkins, L. M. and Donald, A. M. (1997) “Use of the Environmental Scanning Electron Microscopefor the Observation of the Swelling Behavior of Cellulosic Fibres”, Scanning 19, 92-97.

Keywords: environmental scanning electron microscope; cellulosic; fibres; hydration; swelling

Summary: We have developed a method for observing transverse swelling of cellulosic fibers in theenvironmental scanning electron microscope (ESEM). The presence of liquid water in the ESEM specimenchamber allows the observation of in situ hydration without the need for coating, freezing or drying of the sample.For reproducibility of the hydration and dehydration process, specialized mounting techniques are required andcontrol of the conditions for condensation and evaporation of liquid water is necessary. The sensitivity of thesecellulosic materials to the electron beam was investigated, showing that some damage mechanisms are enhancedby the continual presence of water vapor in the chamber. A discussion is presented of the effect of variousexperimental parameters on the extent and time of onset of the damage, and we outline steps to maximize theamount of useful experimental time for these fibers.

382 Ray, Richard; Little, Brenda; Wagner, Patricia and Hart, Kevin (1997) “Environmental ScanningElectron Microscopy Investigations of Biodeterioration”, Scanning 19, 98-103.

Keywords: environmental scanning electron microscopy, biodeterioration; biofilm

Summary: Case studies will be presented in which environmental scanning electron microscopy (ESEM)has been used to provide unique insight into the role of microorganisms in deterioration processes. ESEM is anexcellent tool for demonstrating spatial relationships between microorganisms and substrata because hydrated,nonconducting samples can be viewed with a minimum of manipulation. Copper and iron-rich deposits associatedwith bacteria were detected within corrosion layers on copper and steel surfaces, respectively. Fungal myceliagrowing on wooden storage spools were shown to penetrate protective grease on carbon steel wire rope in contactwith the spool and to cause localized corrosion. Large numbers of marine bacteria were documented within paint



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blisters and disbonded regions of fiber-reinforced polymeric composites. In both cases, it appears that microbialgas production resulted in mechanical damage to the substrata.

383 Roberts, R.A.; Shukla, A.J. and Rice, T. (1997) “Characterization of Polyox® Granules UsingEnvironmental Scanning Electron Microscopy”, Scanning 19, 104-108.

Keywords: environmental scanning electron microscope; hydrophilic polymer; phramaceutical application;Polyox®; granulation

Summary: The scanning electron microscope (SEM) has been frequently used in the pharmaceuticalindustry for studying pharmaceutical products. However, the technique does not allow for the continuouscharacterization of a product in both dry and hydrated states without processing the product. Though the recentadvent of the environmental scanning electron microscope (ESEM), it is now possible to observe a simple in bothdry and hydrated states without extensive product preparation. The ESEM also allows for continual observationduring the hydration process from the dry state until the sample is dissolved. In this study, the ESEM was used tocharacterize the morphologic differences and hydration patterns of granules formulated with a water-solublehydrophilic swelling polymer, Polyox®. Two molecular weights (1,000,000 and 7,000,000) of the polymer wereused in concentrations ranging from 10 to 25% w/w. Visual differences in granule surface morphology anddifferences in hydration patterns were seen in granules prepared from different polymer concentrations. Themorphologic data were corroborated by surface area measurements taken on a surface area analyzer. The rate atwhich the granule dissolved in the ESEM also correlated with the drug dissolution times determined by thestandard USP dissolution method.

384 Hoyberg, Karen (1997) “Environmental Scanning Electron Microscopy of Personal and HouseholdProducts”, Scanning 19, 109-113.

Keywords: acne; environmental scanning electron microscope; skin; fabric; detergent; softeners

Summary: The ability to forego sample preparation and to make observations directly in the environmentalscanning electron microscope has benefited both household and personal product research at Unilever Research.Product efficacy on biological materials such as microcomedones was easily ascertained. Skin biopsies wereexamined in a moist states with no sample preparation. Effects of relative humidity on detergents were visuallydetermined by recreating the necessary conditions in the microscope. Effects of cooling rates on the morphology ofsoftener sheet activities that remained on polyester fabric were characterized via dynamic experimentation.

385 Yeh, C. L.; Kuo, K. K.; Klimkiewicz, M. and Brown, P. W. (1997) “Environmental ScanningElectron Microscopy Studies of Diffusion Mechanism of Boron Particle Combustion” , Scanning 19,114-118.

Keywords: environmental scanning electron microscope; boron; boron oxide; diffusion; dissolution

Summary: This investigation was performed to resolve long-term contradicting theories regarding themechanisms which govern the species diffusion across the liquid B2O3 layer covering a single boron particle duringthe combustion of boron. An environmental scanning electron microscope (ElectroScan E-3) was used to observethe liquefaction characteristics of the boron oxide layer and to examine boron dissolution and species diffusionprocesses in real time. Using a hot stage, crystalline boron particles were heated from 25 to 950oC in O2, H2O, orAr environments. Pure B2O3 particles were also heated in an O2 environment and examined. In situ observationsshowed that the diffusion of dissolved boron into molten B2O3(l) is much more dominant at elevated temperaturesthan the diffusion of gaseous O2 through the B2O3(l) layer. Dissolution of solid boron into the boron oxide layercaused the liquefaction of boron particles at relatively low temperatures (940oC). The chemical composition ofliquid boron oxide, coated on the surface of boron particles, was identified as a polymeric vitreous (BO)n complexthrough the reaction between dissolved boron and molten B2O3(l).

386 Foitzik, Andreas H.; Füting, Manfred W.; Hillrichs, Georg and Herbst, Ludolf-Johannes (1997)“In Situ Laser Heating in an Environmental Scanning Electron Microscope”, Scanning 19, 119-124.



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Keywords: environmental scanning electron microscopy; laser heating; high-temperature behavior;decompostition; carbon fibre-reinforced carbon

Summary: The environmental scanning electron microscope (ESEM) offers improved capabilities forcoupling a scanning electron microscope (SEM) with an in situ laser device compared with conventional SEMs.Such coupling generally enables, for example, the observation of laser glazing effects or high-temperature behavioras well as thermal shock behavior of materials and devices. In an ESEM, decomposition caused by high-temperature gas reactions can additionally be studied while monitoring the gaseous environment online with amass spectrometer attached to the specimen chamber. In this work, we demonstrate the capabilities of an in situlaser system suitable for heating specimen in an in situ deformation stage, thus enabling the further study of themechanical properties of materials far beyond temperatures accomplished by thermal heating stages.

387 Wight, Scott A. (1997) “Better Visualization Inside the Environmental Scanning ElectronMicroscope through the Infrared Chamberscope Coupled with a Mirror”, Scanning 19, 125-126.

Keywords: environmental scanning electron microscope (ESEM); chamberscope

Summary: Clearances are tight inside the specimen chamber of the environmental scanning electronmicroscope (ESEM), and it is difficult to see the relative position \s of detectors and specimens through theviewport. For example, the relative placement of the energy-dispersive spectrometer (EDS) and the specimen iscritical for attaining reasonable x-ray efficiency while protecting the detector window from damage. An infraredchamberscope and mirror attachment were added to improve the visibility inside the chamber.

388 Meredith, P.; Donald, A. M. and Thiel, B. (1996) “Electron-Gas Interactions in the EnvironmentalScanning Electron Microscopes Gaseous Detector”, Scanning 18, 467-473.

Keywords: amplification; charge suppression; electron-gas interactions; environmental scanning electronmicroscope; gaseous detection

Summary: The construction of high signal-to-noise, artifact-free secondary electron image s in the elevatedpressure conditions of an environmental SEM is a nontrivial process. The interactions of information carryingspecies, as well as probe beam electrons, with the chamber gas are the major reasons for such complications. Inthis paper, we discuss and review the present understanding of these phenomena. In addition, we outlineprocedures for assessing the signal-amplifying and charge-neutralizing capabilities of an environmental gas. It isonly with a knowledge of such parameters and an appreciation of the gas-electron collision processes that one canoptimize the microscope’s operating parameters. Moreover, such information enables the separation oftopographic detail form artefactual features in the detected electron images.

389 Newbury, Dale E. (1996) “Imaging Deep Holes in Structures with Gaseous Secondary ElectronDetection in the Environmental Scanning Electron Microscope”, Scanning 18, 474-482.

Keywords: environmental scanning electron microscopy; gaseous secondary electron detector; holes; imageformation; microstructures; scanning electron microscopy

Summary: The gaseous secondary electron detector (GSED) in the environmental scanning electronmicroscope (ESEM) permits collection of electron signals from deep inside blind holes in both conducting andinsulating materials. The placement of the GSED as the final pressure-limiting aperture of the ESEM creates asituation of apparent illumination along the line of sight of the observer. In principle, any point struck by theprimary beam can be imaged. Image quality depends on the depth of the hole. In brass, features at the bottom of a1.5mm diameter hole that was 8mm deep were successfully imaged.

390 Taylor, M. E. and Wight, S. A. (1996) “A New Method for Low-Magnification in theEnvironmental Scanning Electron Microscope”, Scanning 18, 483-489.

Keywords: low magnification; environmental scanning electron microscope; secondary electron detector;pressure-limiting aperture



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Summary: A device has been developed and used successfully on two models of the environmental scanningelectron microscope that allows low-magnification imaging of about 30x, significantly better than the original200x low-magnification imaging limit. This was achieved by using an additional aperture to limit the pressure a ta point where it will not block the electron beam, and a larger aperture plate for the combination finalaperture/secondary electron \signal collection surface that also does not block the electron beam significantly.

391 Paul, B. K. and Klimkiewicz (1996) “Application of an Environmental Scanning ElectronMicroscope to Micromechanical Fabrication”, Scanning 18, 490-496.

Keywords: environmental scanning electron microscope; microelectromechanical systems; microfabrication;additive freeform fabrication; rapid prototyping

Summary: Current advanced methods of micromechanical fabrication require expensive tooling or arerestricted to the fabrication of lateral-shaped microstructures. To overcome these limitations, recent efforts haveused microscale additive freeform fabrication (AFF) methods to prototype micromechanical structures. However,these laser-based methods are limited in resolution. To improve the resolution of microscale AFF methods, anenvironmental scanning electron microscope (ESEM) was used to prototype several electron-beam (EB)-basedmicroscale AFF processes. The results showed that the ESEM is capable of demonstrating process feasibility forEB-based microscale AFF.

392 Pirttiaho, Lauri and Blakely, Jack (1996) “Environmental Scanning Electron MicroscopeObservations of H2S Attack on the Protective Oxide on an Ni-Fe Alloy”, Scanning 18, 497-499.

Keywords: nickel-iron single crystals;epitaxial iron oxide; sulphur attack; corrosion; sufrace steps

Summary: Protective oxide layers on metals are frequently attacked by corroding agents. In this study, theattack of H2S on the protective oxide on 60 wt-%Ni-40 wt%Fe was studied. The oxide layer was prepared in aUHV system and the sulphidation was done in an environmental scanning electron microscope at an elevatedtemperature. The single crystal Ni-Fe sample had a (100) surface which was oxidized by O2 exposure at about 800K to produce an epitaxial Fe2O3 film. The breakup of the oxide was found to begin by pitting along surfacefeatures which are believed to correspond to atomic steps or step bunches. The areas where the oxide was moreuniform were found to show better resistance toward the sulphidation.

393 De Roever, Edmond W. F. and Cosper, David R. (1996) “Fibre Rising and Surface Roughening inLightweight Coated Paper - an Environmental Scanning Electron Microscopy Study”, Scanning 18,500-507.

Keywords: fibre rising; roughness; groundwood pulping; thermomechanical pulping; coating

Summary: Printing with water-based ink may suffer from fiber rising and associated surface roughening dueto the wetting involved. These detrimental changes were stimulated in commercial lightweight coated (LWC)paper by wetting and drying in the environmental scanning electron microscope (ESEM) sample chamber. Mostfibers in the basesheets [made from thermomechancial (TMP) and groundwood] were flat and ribbon-like. Theyswelled upon wetting and shrank upon drying, but remained flat. These changes were reversible. Other fibers werehollow and tube-like. They also expanded upon wetting, but showed different behavior upon drying: (1) flatteningand collapse; or (2) retention of the tube shape, and in some cases, movement of loose fiber ends. Rewettingreturned the fiber ends to a position largely within the sheet surface. Further drying resulted in rising again.Isolated groundwood and TMP fibers with tube shape showed the same types of contrasting behavior, that is,collapse upon drying or retention of the tube shape. From these observations we conclude that fiber rising islimited to comparatively stiff fibers that maintain their shape upon wetting or drying. Rising occurred duringdrying, not during wetting and swelling. Fiber rising might be avoided by eliminating the tube-like fibers, or burfurther refining to reduce their stiffness to an acceptable level. As evidence of this, we observed that some of theTMP fibers collapsed upon drying instead of showing rising. Fiber rising was thus observed here in fibers whichretain their tube-like shape (despite refining and calendering) and not, as suggested in the literature, in ribbon-likefibers returning to an un-collapsed tube-like shape when wetted. Fiber rising was less common in the sheets that



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expected from the strong gloss reduction and surface roughening of the LWC paper seen upon wetting (outside theESEM),\. In other words, gloss reduction and roughening may be caused in part by processes other than fiberrising. Roughening might also result from the association of flat and tube-like fibers in the sheet. Tube-like fibersswell radially (vertically) much more than do flat, collapsed fibers, which leads to thin zones in the coating overthe raised fibers and coating cracks along their edges. These types of damage of the coating were quite common.This mode of sheet roughening foes not require fiber rising in the strict sense, that is, rising of fiber ends out of thesheet surface but the tube-like fibers causing it might show fiber rising at their tails to some extent.

394 Rao, Sudeep M.; Brinker, C. Jeffrey and Ross, Timothy J. (1996) “Environmental Microscopy inStone Conservation”, Scanning 18, 508-514.

Keywords: environmental microscopy; stone preservation; weathering protection

Summary: The natural weathering of stone is accelerated by the combined effects of acid rain, saltcrystallization, and the freeze-thaw cycles of water. Since weathering will take place until the system reacheschemical equilibrium, we can mitigate the loss to historic stone monuments and structures by treatments of thestone that retard hydrolysis and impart mechanical strength. While macroscopic studies of stone weathering havebeen performed addressing the causes, the reactions, and the kinetics involved, the mechanisms of weathering, andthe chemical remediation of stone need to be better understood at a microscopic level. Our approach usesenvironmental scanning electron microscopy where sample can be imaged in their wet, natural state, thusfacilitating the in situ study of the weathering processes. The environment in the microscope is set up to stimulatethe conditions of degradation by introducing corrosive liquids and gases and varying the temperature, pressure, andwater content in the environmental chamber of the microscope. In this study, we observed specimens of limestone,treated calcite, and sandstone. We have characterized the morphology, structure and chemical constituents of thesamples for comparison at a later stage when protective coating will be applied. In situ leaching tests wereperformed on limestone samples to study the mechanisms of degradation. Granular disintegration due to leachingof the binding material between the grains was seen. We have also observed , in situ, the changes in the structureof sodium sulphate, used in salt crystallization tests, during hydration and dehydration cycles; it changed from thatof dense grains to hydrated mesoporous granules with the generation of new surface area.

395 Neubauer, C. M. and Jennings, H. M. (1996) “The Role of the Environmental Scanning ElectronMicroscope in the Investigation of Cement-Based Materials”, Scanning 18, 515-521.

Keywords: cements; deformation; hydration; microstructure; properties

Summary: The role of the environmental scanning electron microscope (ESEM) in the study of cement-based materials is reviewed. Since water is an intrinsic part of the microstructure of cement paste, techniques thatfacilitate the study of wet specimens are necessary. The evolution of techniques is traced from standardmicroscopic methods to the use of the ESEM for in situ analysis. The importance of past and current work isdiscussed, including novel analytical methods designed for the study of cement pastes. Directions for future workare also discussed.

396 D’Emanuele, Anthony and Gilpin, Christopher (1996) “Applications of the EnvironmentalScanning Electron Microscope to the Analysis of Pharmaceutical Formulations”, Scanning 18, 522-527.

Keywords: environmental scanning electron microscope; pharmaceutical applications; polymers;formulations

Summary: Electron microscopy has been used for several years as a routine tool for the study ofpharmaceutical formulations. However, it is usually desirable to obtain information on these systems in the wetstates, and there are concerns regarding the interpretation of information provided by conventional electronmicroscopy where samples are subjected top preparation techniques which may include freezing, drying, fracturingand coating. The environmental scanning electron microscope (ESEM) has been used to analyze a number ofpharmaceutical samples in their natural state. Results obtained from these samples, including biodegradable



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matrices, microparticulate systems (both degradable and non-biodegradable), and bioadhesive matrices, will bediscussed and the merits and limitations of the ESEM will be highlighted.

397 Connolly, Jon H.; Chen, Ying and Jellison, Jody (1995) “Environmental Scanning ElectronMicroscopic Observation of the Hyphal Sheath and Mycofibrils in Postia placenta”, CanadianJournal of Microbiology 41, 433-437.

Keywords: mycofibrils; hyphal sheath, environmental scanning electron microscopy; extracellular matrix

Summary: Environmental scanning electron microscopic observations of Postia placenta grown on a definedmedium and on red spruce wood allowed for the examination of the hydrated sheath of P. placenta. In the woodenvironment, mature hyphae that were not adhering to the substrate were observed to have a mycofibrillarmorphology whereas hyphal tips and branch points had a smooth sheath morphology. A mycofibrillar adhesivematrix was observed on the hyphae growing on glass slides in the defined medium. These morphologies forhyphal sheaths in P. placenta are similar to those previously described by investigators from other laboratories whohave used traditional electron microscope preparative protocols that include dehydration steps. The potential futureusefulness of environmental scanning electron microscopic technology in the study of the fine details ofextracellular matrices is briefly discussed.

398 Connolly, Jon H. and Jellison, Jody (1995) “Calcium translocation, calcium oxalate accumulation,and hyphal sheath morphology in the white-rot fungus Resinicium bicolor”, Canadian Journal ofBotony 73, 927-936.

Keywords: calcium oxalate; hyphal sheath; environmental scanning electron microscopy

Summary: The white-rot fungus Resinicium bicolor was cultured on wood blocks in a modified soil blockassay and was observed by environmental scanning electron microscopy and scanning electron microscopy.Resinicium bicolor was found to translocate calcium in mycelial cords in quantities greater than that found in thewood blocks and accumulated this calcium in the form of calcium oxalate. Calcium oxalate crystal clusters ofmycelial cords were 3x larger and far more numerous than the crystal clusters produced by the same fungus withinthe wood. Environmental scanning electron microscopy technology allowed for the examination of the hyphalsheath in a hydrated state. The hydrated hyphal sheath was found to be much thicker than the desiccated sheatheobserved after standard scanning electron microscope preparations. Calcium oxalate crystals were found to beembedded in the thick hyphal sheathe, suggesting that previous observations of within-wall calcium oxalateprecipitation may perhaps be better interpreted as artifacts generated during sample preparation.

399 Stanislawska, Anna and Lepoutre, Pierre (1995) “Effect of Pigment Shape, Binder Content andDewatering Conditions on the Consolidationof Pigmented Coatings”, Proceedings of the 22ndWaterborne, High-Solids & Powder Coatings Symposium, New Orleans, LA, 386-395

Keywords:

Summary: The consolidation of pigmented coatings based on clay or ground calcium carbonate and latex,and formulated above the critical pigment volume concentration (CPVC), was examined buy quenching the wetcoatings at various stages of drying in liquid Nitrogen and freeze-drying (F-D). From SEM examination of the F-D coatings and measurements of gloss, void fraction, surface area and light-scattering, the process of developmentof the porous structure could be followed. The overall process is basically the same, independent of pigment shapeand latex content: Formation of a loose structure with large voids, at a first critical concentration where particlealignment at the surface is maximum and void size is smallest; coalescence of the latex, in the presence of water,accompanied by a decrease in surface area and a shrinkage that depends on the latex content and it rhelogicalcharacteristics and by an increase in pore size; emptying of pores after a second critical concentration. Pigmentshape was found to affect the consolidation process. Gloss of the all-clay structures was always much higher thanfor CaCO3. Pore sizes at all stages of the consolidation were smaller with clay than with rhombic CaCO3. Intensedrying increased the shrinkage of all coatings but thermal post-treatment of room temperature-dried coatings hadno effect on dimensions.



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400 Stanislawska, Anna and Lepoutre, Pierre (1995) “Development of Porous Structure During Dryingof Pigmented Coatings”, Proceedings of the American Chemical Society Division of PolymericMaterials: Science and Engineering, Chicago, IL, 55-56

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Summary:

401 Al-Turaif, H.; Unertl, W. N. and Lepoutre, P. (1995) “Effect of pigmentation on the surfacechemistry and surface free energy of paper coating binders”, Journal of Adhesion Science andTechnology, 9 (7), 801-811

Keywords: coatings; pigment; binder; surface energy; surface chemistry; morphology; clay; latex; watersoluble polymer; contact angle; acid0base; gloss; profilometry; EDS; XPS.

Summary: The effect of the addition of clay and TiO2 pigments on the surface energy and surface chemistryof films made from polymers used in paper coating formulations was evaluated. The polymers were carboxymethylcellulose, polyvinyl alcohol and a protein-based polymer - all water soluble - and two styrene-butadiene latexes ofdifferent carboxylation levels. The morphology of the surfaces was characterized by SEM examination, glossmeasurement and stylus profilometry. Chemical composition was determined by EDS and XPS techniques.Surface energy and its Lifshitz-van der Waals and acid-base components were obtained from contact anglemeasurements using the van Oss et al. approach. Even though the addition of pigment increasingly upset theplanar surface of the films, their surface chemistry and surface energy were only slightly affected over thepigmentation range studied (up to 40% by volume) and were dominated by the characteristics of the binderpolymer.

402 Dickson, Robert J. “Adhesion and Cohesion in Coated Paper”

Keywords:

Summary:

403 Forsberg, P. “Environmental Scanning Electron Microscope (ESEM)”, Surface Analysis of Paper -ed. T. Crunes, 63-68

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Summary:

404 Smith, David A. (1996) “Some Applications of Electron Optical Techniques to Materials forInterconnects”, Scandem ‘96 - Aarhus

Keywords:

Summary:

405 Smith, David A.; Small, Martin and Stanis, Carol (1993) “Electron microscopy of the grainstructure of metal films and lines”, Ultramicroscopy 51, 328-338

Keywords:

Summary: The demands of the ULSI in the sub-micron regime require the understanding of properties andcontrol of microstructure in a situation where one or more of the characteristic dimensions of the sample is of thesame order as the grain size of the material. Grain structure, as determined by deposition conditions, samplegeometry and thermal treatment during processing, remains the first-order microstructural factor governing theproperties. The grain structure evolves during both deposition and processing. A major practical and scientificissue is the elucidation of the conditions which will result in a stable grain structure. This happens when the forcesacting on the grain boundaries are in equilibrium.



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406 Groom, Leslie H.; Shaler, Stephen M. and Mott, Laurence (1995) “Characterizing Micro- andMacro- Mechanical Properties of Single Wood Fibers”, 1995 International Paper PhysicsConference, 13-22

Keywords:

Summary: Tensile micro and macromechanical properties of individual wood fibers were ascertained usinga miniature tensile tester with a custom gripping assembly. Macromechanical properties were derived from virginfibers of a plantation grown lobolly pine (Pinus taeda L.). Also tested were various commercially-hydrapulpedrecycled fiber types. Confocal laser scanning microscopy was used to determine cross-sectional areas of severalfiber types and load-elongation curves for single fibers were converted to stress-strain curves. Data was assembledto determined the regions of a tree that produce fibers with superior load carrying capacity. Preliminary findingsindicate superior virgin fibers exist toward the outer growth rings, and neat the center of the merchantable trunklength. Virgin fibers may have superior macromechanical properties compared to recycled fibers.Micromechanical properties of the wood cell wall were also empirically quantified for the first time. A techniquewas developed to acquire high quality images of fibers under uniaxial tensile strain in an environmental scanningelectron microscope (ESEM). Images were used to perform a digital image correlation, full-field strainassessment, in the regions surrounding various natural and induced defects such as microcompressions, borderedpits and creases. The system proved useful for measuring cell wall displacement to within +/- 8nm (0.1 pixel) andboth longitudinal (εγγ) and transverse strains (εχχ) with a 0.3% tolerance.

407 Mott, Laurence; Shaler, Stephen M. and Groom, Leslie H. “Micro-strain distributions and defectsin single wood-pulp fibers”, Department of Forest Management. Forest Products Laboratory, 5755Nutting Hall, University of Maine, Orono, ME 04469-5755 / USDA Forest Service, SouthernResearch Station. 2500 Shreveport Hwy, Pineville, LA 71360

Keywords:

Summary: Efficient utilization of wood pulp relies on a thorough understanding single fiber mechanicalresponse. The stretching of single fibers in uniaxial tension was directly visualized in an environmental scanningelectron microscope. Crack imitation, crack growth, and complex mixed-mode failure sequences were observed.Whole-field microstrain measurements of structurally defect-free and defective cell wall material were made usinga digital image correlation technique with a +/- 0.008 micrometer resolution. Results indicate single fibers exhibita strain concentration banding effect similar to that of some metals. Damage in the form of localized plasticdeformation may accumulate in bordered pit regions under small applied strains (<0.5%) previously thought topromote only a purely elastic response in wood fiber cell wall material.

408 Griffin, Brendan J. (1997) “Field of view and image distortion : A review of low magnificationimaging in the environmental and conventional scanning electron microscopes (SEM)”, Microscopyand Microanalysis, 3 (2), 1193-4

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Summary:

409 Thiel, B. L.; Fletcher, A. L. and Donald, A. M. (1997) “Comparison of amplification and imagingbehaviours of several gases in the environmental SEM”, Microscopy and Microanalysis, 3 (2), 1195-6

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Summary:

410 Griffin, Brendan J. (1997) “A new mechanism for the imaging of crystal structure in non-conductive materials: An application of charge-induced contrast in the environmental scanningelectron microscope (ESEM)”, Microscopy and Microanalysis, 3 (2), 1197-8



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Keywords:

Summary:

411 Bache, I. C.; Thiel, B. L.; Stelmashenko, N. and Donald, A. M. (1997) “Transport of secondaryelectrons through a film of condensed water: Implications for imaging wet samples”, Microscopyand Microanalysis, 3 (2), 1199-1200

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412 Carlton, R. A.; Orton E. and Lyman, C. E. (1997) “Application of ESEM/EDS to pharmaceuticalsynthesis”, Microscopy and Microanalysis, 3 (2), 1201-1202

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413 Li, M. J. and Taylor, M. E. (1997) “Characterization of contamination effects on polyimide filmfracture using environmental scanning electron microscope”, Microscopy and Microanalysis, 3 (2),1203-4

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414 Gilpin, C. J. (1997) “Biological applications of environmental scanning electron microscopy”,Microscopy and Microanalysis, 3 (2), 1205-6

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415 Mansfield, John (1997) “Review of techniques for overcoming XEDS problems in the environmentalscanning electron microscope”, Microscopy and Microanalysis, 3 (2), 1207-8

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416 Wight, Scott; Gillen, Greg and Herne, Tonya (1997) “Environmental SEM electron damageimaging of self assembled monolayers with SIMS”, Microscopy and Microanalysis, 3 (2), 1209-10

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Summary:

417 Bache, I. C.; Kitching, S.; Thiel, B. L. and Donald, A. M. (1997) “Variations in the probe beambroadening with operating conditions in the ESEM: Monte-Carlo simulations and EDXmeasurements”, Microscopy and Microanalysis, 3 (2), 1211-2

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Summary:

418 Wight, S. A.; Cavicchi, R. E.; Nystrom, M. J. and DiMeo, F. (1997) “Microhotplate chemical vapordepositioon and in the environmental SEM chamber”, Microscopy and Microanalysis, 3 (2), 603-4

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419 Bache, I. C.; Anderson, V. J.; Jones, R. A. L. and Donald, A. M. (1997) “The observation ofhierarchical structures in biopolymer phase separation: novel ESEM contrast mechanisms”,Microscopy and Microanalysis, 3 (2), 605-6

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420 Mutlu, I. H.; Goddard, R. E. and Hascicek, Y. S. (1997) “ESEM hot stage evaluation of sol-gelinsulation coatings for high field HTS magnets”, Microscopy and Microanalysis, 3 (2), 607-8

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Summary:

421 Thiel, B. L.; Hussein-Ismail, M. R. and Donald, A. M. (1997) “Effects of space charge on ESEMgas amplification”, Microscopy and Microanalysis, 3 (2), 609-10

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Summary:

422 Doehne, Eric (1997) “ESEM and video microscopy studies in stone conservation”, Microscopy andMicroanalysis, 3 (2), 613-4

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Bibliography

INDEX

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Bestandsnaam: ESTUTOR.docMap: C:\handleiding\newSjabloon: C:\WINWORD\TEMPLATE\estutor.dotTitel: What is an ESEM - Brief benefits summary with attention grabbing examplesOnderwerp:Auteur: MarkTrefwoorden:Opmerkingen:Aanmaakdatum: 19-05-98 15:05Wijzigingsnummer: 10Laatst opgeslagen op: 19-05-98 18:06Laatst opgeslagen door: markTotale bewerkingstijd: 94 minutenLaatst afgedrukt op: 20-05-98 11:52Vanaf laatste volledige afdruk

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ENVIRONMENTAL SCANNING ELECTRON MICROSCOPY

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