1 Introduction of Microscopy and Microanalysis (1) Dr. Chunlei Wang Oct 14, 2009 SEM Pictures Copyright@peggy wang Instructor: Dr. Chunlei Wang Instructor: Dr. Chunlei Wang Office hours: Tue and Thu 11:00 Office hours: Tue and Thu 11:00- 12:00 12:00 Office location: EC 3463 Office location: EC 3463 Reference books: Reference books: (1) (1) Electron Microscopy and Analysis (3 Electron Microscopy and Analysis (3 rd rd edition) by Peter edition) by Peter J. J. Goodhew Goodhew, John Humphreys, and Richard , John Humphreys, and Richard Beanland Beanland, , Taylor&Francis Taylor&Francis , 2001 , 2001 (2) (2) Transmission Electron Microscopy (I) Basics, by David Transmission Electron Microscopy (I) Basics, by David B.Williams B.Williams and C. Barry Carter, Springer, 1996 and C. Barry Carter, Springer, 1996 SEM Lab: Oct 16 and Oct 25, 1:00 SEM Lab: Oct 16 and Oct 25, 1:00- 3:00pm 3:00pm TEM Lab: end of Nov TEM Lab: end of Nov Grading: Grading: Two Two homeworks homeworks (40%) + One final written exam (60%) (40%) + One final written exam (60%)
Transcript
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Introduction of Microscopy and Microanalysis (1)
Dr. Chunlei WangOct 14, 2009
SEM Pictures Copyright@peggy wang
�� Instructor: Dr. Chunlei WangInstructor: Dr. Chunlei WangOffice hours: Tue and Thu 11:00Office hours: Tue and Thu 11:00--12:0012:00Office location: EC 3463Office location: EC 3463
�� Reference books: Reference books: (1)(1) Electron Microscopy and Analysis (3Electron Microscopy and Analysis (3rdrd edition) by Peter edition) by Peter
J. J. GoodhewGoodhew, John Humphreys, and Richard , John Humphreys, and Richard BeanlandBeanland, , Taylor&FrancisTaylor&Francis, 2001, 2001
(2)(2) Transmission Electron Microscopy (I) Basics, by David Transmission Electron Microscopy (I) Basics, by David B.WilliamsB.Williams and C. Barry Carter, Springer, 1996and C. Barry Carter, Springer, 1996
�� SEM Lab: Oct 16 and Oct 25, 1:00SEM Lab: Oct 16 and Oct 25, 1:00--3:00pm3:00pm�� TEM Lab: end of NovTEM Lab: end of Nov�� Grading: Grading:
Two Two homeworkshomeworks (40%) + One final written exam (60%)(40%) + One final written exam (60%)
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Why microscopy and microanaylsis?Why microscopy and microanaylsis?
Typical cleanroom equipments:
� Photolithography tools� Thin film deposition and material growth � Dry etching � Wet etching � Furnaces and ovens � Packaging � Sample preparation � Analytical equipment
� Critical dimension measurements of small features� Topography and 3D microstructure� Qualitative identification and quantitative elemental information� Chemical composition and compositional profile� Defect and impurity� …
Optical MicroscopyScanning Electron Microscopy (SEM)Transmission Electron Microscopy (TEM)Scanning Probe Microscopy (AFM, STM)Energy Dispersion X-ray Spectroscopy (EDS)X-ray Diffraction Spectroscopy (XRD)Photoelectron Spectroscopy (XPS, UPS) Auger Electron Spectroscopy (AES)Electron Energy Loss Spectroscopy (EELS)Rutherford Backscattering Spectroscopy (RBS)Focused Ion Beam (FIB)Secondary Ion Mass Spectrometry (SIMS)Mass Spectrometry (MS)Nuclear Magnetic Resonance spectroscopy (NMR)Photoluminescence Spectroscopy (PL)Cathodoluminescence Spectroscopy (CL)Raman Spectroscopy Infrared spectroscopy (IR, FTIR)
First Place, Nikon's Small World 1995 Competition, Christian Gautier, Larva of Pleuronectidae (20x), RheinbergIllumination and Polarized Light
• Easy to use• Samples in air or water• Total magnification: ×100-1000product of the magnifications of the ocular lens and the objective lens• Image processing by CCD
Ocular (eyepiece)
Objective
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Brief HistoryBrief History
Thomas Young (1773-1829)
• In 1801, Thomas Young passed a beam of light through
two parallel slits in an opaque screen, forming a pattern of
alternating light and dark bands on a white surface beyond.
This led Young to reason that light was composed of waves.
wave theory of light
Brief HistoryBrief History
Sir Joseph John Thomson
(1856-1940)
Nobel prize 1906
Thomson’s 2nd Cathode ray experiment
• In 1897, J.J.Thomson discovered “corpuscles”, small
particles with a charge/mass ratio more than 1000 times
greater than that of protons, swarming in a sea of positive
charge (“plum pudding model”).
Discovery of the ELECTRON
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Brief HistoryBrief History
�� In 1924, Louis de Broglie first theorized that the electron had In 1924, Louis de Broglie first theorized that the electron had wavewave--like characteristics. Application of the idea of particle like characteristics. Application of the idea of particle –– wave wave dualism (only known for photons up to then) for any kind of dualism (only known for photons up to then) for any kind of matter. (first person to receive a Nobel Prize on a PhD thesis )matter. (first person to receive a Nobel Prize on a PhD thesis )
Louis Victor de Broglie (1892-1987)
Nobel prize 1929
mv
h
p
h==λ
Electron=Particle & Wave
�� In 1926, Hans Busch discovered that magnetic fields could act asIn 1926, Hans Busch discovered that magnetic fields could act as
lenses by causing electron beams to converge to a focus (electrolenses by causing electron beams to converge to a focus (electron n
lens). lens).
Brief HistoryBrief History
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Brief HistoryBrief History
�� In 1927, Davisson and In 1927, Davisson and GermerGermer, Thomson and Reid, , Thomson and Reid,
independently carried out their classic electron diffraction independently carried out their classic electron diffraction
experiments (demonstration of wave nature of electrons) experiments (demonstration of wave nature of electrons)
Sir George Paget Thomson
(1892 – 1975)
Nobel Prize: 1937
(shared with C.J. Davison)
GP Thomson Experimental Apparatus and Results
Electron=Wave
Interference peak
Electron gun
Ni Crystal
detector
θ
I(θ)
θ0 60o
Davisson-Germer experiment
�� In 1931, Knoll (inventor of SEM, 1935) and Ruska coIn 1931, Knoll (inventor of SEM, 1935) and Ruska co--invent invent
electron microscope and demonstrated electron images. electron microscope and demonstrated electron images.
Brief HistoryBrief History
Max Knoll
(1897-1969)
Ernst Ruska
(1906-1988)
Nobel Prize 1986 Knoll and Ruska co-invent electron microscope
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�� 1938: M. von Ardenne: 1st STEM1938: M. von Ardenne: 1st STEM
�� 1936: the Metropolitan Vickers EM1, first 1936: the Metropolitan Vickers EM1, first commericalcommerical TEM, UKTEM, UK
�� 1939z: regular production, Siemens and 1939z: regular production, Siemens and HalskeHalske, Germany, Germany
�� After World War II: Hitachi, JEOL, Philips, RCA, etcAfter World War II: Hitachi, JEOL, Philips, RCA, etc
�� 1945: 1nm resolution1945: 1nm resolution
�� 1949: 1949: HeidenreichHeidenreich first thinned metal foils to electron transparencyfirst thinned metal foils to electron transparency
�� Cambridge group developed the theory of electron diffraction Cambridge group developed the theory of electron diffraction contrastcontrast
�� Thomas pioneered the practical applications of the TEM for the Thomas pioneered the practical applications of the TEM for the solution of materials problems (1962)solution of materials problems (1962)
�� …………
Brief HistoryBrief History
Optical vs. Electron Microscopy
Copyright2005@CARL ZEISS SMT
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SEMSEMSEMSEMSEMSEMSEMSEM
� SEM permits the observation and characterization of heterogeneous organic and inorganic materials on a nm to µm scale.� Imaging capabilities � elemental analysis
� In the SEM, the area to be examined or the microvolume to be analyzed is irradiated with a fine focused electron beam, which may be swept in a raster across the surface of the specimen to form images or maybe static to obtain an analysis at one position.
� The types of signals produced from the interaction of electron beam with the sample include secondary electrons, backscattered electrons, characteristic x-rays, and other photons of various energies.
(a) Optical micrograph of the radiolarian Trochodiscuslongispinus. (b) SEM micrograph of same radiolarian.
(Taken from J.I. Goldstein et al., eds., Scanning Electron Microscopy and X-Ray Microanalysis, (Plenum Press,NY,1980).)
(a) (b)
Optical vs. Electron Microscopy
� Depth of Focus� Resolution
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Why electrons?
� Wave Behaviors
– images and diffraction patterns
– wavelength can be tuned by energies
� Charged Particle Behaviors
– strong electron-specimen interactions
– chemical analysis is possible
e-
e-
� Optical microscope: 400-700nm, resolution?� Electron microscope: ?
Light
• p = h/λ λ λ λ (matter also)
• p = E/c
• E = hf = hc/λ
Matter
• p = h/λ λ λ λ (light also)
•
• E = h2/2mλ2mE2p =
h: planck’s constant
electrongun
Ni Crystal
detector
θ
� In 1927-8, it was shown (Davisson-Germer) that, like x-rays, ELECTRONS can also diffract off crystals !
I(θ)
θ
Interference peak !
0 60o
Electrons can act like waves!!Electrons can act like waves!!Electrons can act like waves!!Electrons can act like waves!!Electrons can act like waves!!Electrons can act like waves!!Electrons can act like waves!!Electrons can act like waves!!
Particles as wavesParticles as wavesParticles as wavesParticles as wavesParticles as wavesParticles as wavesParticles as wavesParticles as waves
� What size wavelengths are we talking about? Consider a photonwith energy 3 eV, and therefore momentum p = 3 eV/c. Its wavelength is:
�� What is the wavelength of an What is the wavelength of an electronelectron with the same momentum? with the same momentum?
λλee = = h/ph/peeSame relation for particles and photons.
Compared to the energy of the photon (given above):Compared to the energy of the photon (given above): eVpcE 3==
�� Note that the kinetic energy of the electron is different from tNote that the kinetic energy of the electron is different from the energy of he energy of the photon with the same momentum (and wavelength):the photon with the same momentum (and wavelength):
( )
eV.eV/J.
J.)m)(kg.(
sJ.
m
h
m
pKE
619
24
2931
234
2
22
1088106021
1041110414101192
106256
22
−−
−
−−
−
×=×÷
×=××
⋅×===
λ
( ) ( ) nms/ms.ceV
seV.
p
h4141031041
3
10144 81515
=×××=×⋅×
== −−
λ
Matter wavelengths
� The DeBroglie wavelength of an electron is inversely related to the electron momentum:
Wavelength of an Electron
λ = h/p
� Frequently we need to know the relation between the electron’s wavelength and its kinetic energy E.
p and E are related through the classical formula:2
-31
e
2-15
2
pE m 9 .11 10 kg
2m
hE h 4 .14 10 eV s
2m
= = ×
= = × ⋅λ
nmeV .
E2
25051
λ
⋅= E in electron volts
λ in nanometers
λ
nmeV Ephoton
⋅=
1240DonDon’’t confuse witht confuse with for a for a
photon !photon !
p = h/λ
For m = me: (electrons)
always true!
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Application of Matter Waves: Application of Matter Waves: Application of Matter Waves: Application of Matter Waves: Application of Matter Waves: Application of Matter Waves: Application of Matter Waves: Application of Matter Waves: Electron Electron Electron Electron Electron Electron Electron Electron MicroscopyMicroscopyMicroscopyMicroscopyMicroscopyMicroscopyMicroscopyMicroscopy
�� The ability to The ability to ““resolveresolve”” tiny objects improves as the wavelength decreases. tiny objects improves as the wavelength decreases. Consider the microscope objective: Consider the microscope objective:
A good microscope objective has f/D A good microscope objective has f/D ≅≅ 2, so with 2, so with λ ~ 500 nm ~ 500 nm the optical microscope has a resolution of the optical microscope has a resolution of ddminmin ≅≅ 1 1 µµmm. .
D
f.fd cmin λα 221=≈
Critical angle for resolution:
We can do much better with matter waves because, as we shall seeWe can do much better with matter waves because, as we shall see, electrons , electrons with energies of a few with energies of a few keVkeV have wavelengths less than 1 nm.have wavelengths less than 1 nm.
The instrument is known as an The instrument is known as an ““electron microscopeelectron microscope””..
The minimum d for which we
can still resolve two objects
is ααααc times the focal length:Dc
λα 22.1=
Objects to be resolved
diffraction disks
D
αα
d
f(not interference maxima)
= focal length of lens if image plane is at a large distance.
�� Electron Microscopy of a Virus:Electron Microscopy of a Virus:
You wish to observe a virus with a diameter of 20 nm, which is You wish to observe a virus with a diameter of 20 nm, which is much too small to observe with an optical microscope. much too small to observe with an optical microscope. Calculate Calculate the voltage requiredthe voltage required to produce an electron to produce an electron DeBroglieDeBrogliewavelength suitable for studying this virus with a resolution ofwavelength suitable for studying this virus with a resolution ofddminmin = 2 nm= 2 nm. The . The ““ff--numbernumber”” for an electron microscope is quite for an electron microscope is quite large: large: f/D f/D ≈≈ 100100. .
Imaging a Virus*
object
Electron
optics
D
f
electron gun
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SolutionSolution
( )eVk .
nm .
nmeV .
m
hE 65
01640
5051
22
2
2
2
=⋅
==λ
D
f.dmin λ221≈
nm .f.
Dnm
f.
Ddmin 01640
2212
221=
=
≈λ
To accelerate an electron to an energy of 5.6 keV requires 5.6 kilovolts
�� Electron Microscopy of a Virus:Electron Microscopy of a Virus:
You wish to observe a virus with a diameter of 20 nm, which is You wish to observe a virus with a diameter of 20 nm, which is much too small to observe with an optical microscope. much too small to observe with an optical microscope. Calculate Calculate the voltage requiredthe voltage required to produce an electron to produce an electron DeBroglieDeBrogliewavelength suitable for studying this virus with a resolution ofwavelength suitable for studying this virus with a resolution ofddminmin = 2 nm= 2 nm. The . The ““ff--numbernumber”” for an electron microscope is quite for an electron microscope is quite large: large: f/D f/D ≈≈ 100100. .
object
Electron
optics
D
f
electron gun
ResolutionResolution
�� For 100keV electron, we can find that For 100keV electron, we can find that λλ~4pm (0.004 nm)~4pm (0.004 nm)
�� We are nowhere near building We are nowhere near building TEMsTEMs that approach this that approach this wavelength limit of resolution, because we canwavelength limit of resolution, because we can’’t make t make perfect electron lenses.perfect electron lenses.
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HVEMHVEM
�� HVEMsHVEMs: High Voltage Electron Microscopes: High Voltage Electron Microscopes
�� 1980s: only one HVEM (1MV)1980s: only one HVEM (1MV)
�� 1990s: three 1.25 MV machines1990s: three 1.25 MV machines
�� Intermediate voltage electron microscopes (Intermediate voltage electron microscopes (IVEMsIVEMs) were ) were introduced in the 1980s. (300introduced in the 1980s. (300--400 kV)400 kV)
UltraUltra--High Voltage Electron High Voltage Electron
MicroscopyMicroscopy
The Research Center for Ultra-High Voltage Electron Microscopy was established in 1974 in Osaka University, Japan. The main purpose of this center is to utilize for scientific research a 3-MV class ultrahigh voltage electron microscope, which was originally installed in 1972 and renewed in 1995 through financial aid from the Ministry of Education
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�� What happens when the beam reaches the specimen?What happens when the beam reaches the specimen?
�� How the signals produced by the EBHow the signals produced by the EB--specimen interactions are converted specimen interactions are converted into images and/or spectra that convey useful information?into images and/or spectra that convey useful information?�� Size, shape, composition, certain properties, etc.Size, shape, composition, certain properties, etc.
It is critical to understand the physics of electron beam-specimen interactions
Monte Carlo Simulation of Electron Beam-Specimen Interactions
by David Joy and are based on the algorithms described in the book "Monte Carlo Modeling
for Electron Microscopy and Microanalysis" published by Oxford University Press (1995).
Interaction of high energy (~kV) electrons Interaction of high energy (~kV) electrons Interaction of high energy (~kV) electrons Interaction of high energy (~kV) electrons Interaction of high energy (~kV) electrons Interaction of high energy (~kV) electrons Interaction of high energy (~kV) electrons Interaction of high energy (~kV) electrons with (solid) materialswith (solid) materialswith (solid) materialswith (solid) materialswith (solid) materialswith (solid) materialswith (solid) materialswith (solid) materials
� Secondary electrons are specimen electrons that obtain energy by inelastic collisions with beam electrons. They are defined as electrons emitted from the specimen with energy less than 50ev.
� Secondary electrons are predominantly produced by the interactions between energetic beam electrons and weakly bonded conduction-band electrons in metals or the valence electrons of insulators and semiconductors. There is a great difference between the amount of energy contained by beam electrons compared to the specimen electrons and because of this, only a small amount of kinetic energy can be transferred to the secondary electrons.
– Elastic scattering which causes backscattering of electrons without loss of kinetic energy. This is particularly important in SEM.
– Inelastic scattering which results in transfer of energy from the beam electrons to the sample’s. This leads to generation of secondary electrons: Auger, X-rays, electron-hole pairs in conductors and insulators, long wavelength electromagnetic radiation or cathodoluminecence (vis, UV, IR), lattice vibrations (phonons), electron oscillations in metals (plasmons).
----------------Visualizing the interaction volume
•The interaction volume can be observed in certain plastic materials such as PMMA
•Undergo Molecular bonding damage during electron bombardment that renders the material sensitive to etching in a suitable solvent
•This phenomenon is the basis for EB lithography
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Electron BeamElectron Beam--Specimen InteractionsSpecimen Interactions• EB lithography
Kartikeya Malladi, Chunlei Wang, and Marc Madou, “Microfabrication of Suspended C-MEMS
structures by EB Writer and Pyrolysis”, Carbon, 44(13), (2006) 2602-2607
SEMSEMSEMSEMSEMSEMSEMSEM
�� High voltage electrons hit the sample and reflect offHigh voltage electrons hit the sample and reflect offElastic collisions, determine angles of reflectionElastic collisions, determine angles of reflection
�� Interference from electrons at different angles create contrastInterference from electrons at different angles create contrast�� Focus beam reflection onto a larger imageFocus beam reflection onto a larger image�� Retains orientation and phase informationRetains orientation and phase information�� Visualization of sample, with theoretical 1 Visualization of sample, with theoretical 1 ÅÅ resolution resolution �� Surface topography if low energy secondary electrons are Surface topography if low energy secondary electrons are
collectedcollected�� Atomic number or orientation information if higher energy Atomic number or orientation information if higher energy
backscattered electrons are used for imagingbackscattered electrons are used for imaging�� Differentiation between surface roughness, porosity, granular Differentiation between surface roughness, porosity, granular
deposits, stressdeposits, stress--related gross related gross microcracksmicrocracks (often used in (often used in conjunction with conjunction with microsectioningmicrosectioning))
�� Observation of grain boundaries in Observation of grain boundaries in unetchedunetched samplessamples�� Critical dimension measurementsCritical dimension measurements
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HomeworkHomeworkHomeworkHomeworkHomeworkHomeworkHomeworkHomework� What is the basic principle of a Confocal Microscope?
Drosophila melanogaster, FITC
non-confocal
confocal 3D projection
NikonNikon’’s Small World Gallerys Small World Gallery
First Place, 2007 Competition
Gloria Kwon
Memorial Sloan-Kettering InsitituteNew York City, New York, USADouble transgenic mouse embryo, 18.5 days (17x)Brightfield, Darkfield, Fluorescence
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NikonNikon’’s Small World Gallerys Small World Gallery
Second Place, 2007 Competition
Michael Hendricks
Temasek Life Sciences LaboratoryNational University of SingaporeKent Ridge, SingaporeZebrafish embryo midbrain and diencephalon (20x)Confocal
