15
Functional Nanostructures Processing, Characterization, and Applications
Functional NanostructuresProcessing, Characterization,and Applications
Nanostructure Science and Technology
Series Editor: David 1. Lockwood, FRSCNational Research Council ofCanadaOttawa, Ontario, Canada
Currentvolumes in this series:
Functional Nanostructures: Processing, Characterization, and ApplicationsEdited by Sudipta Seal
Nanotechnology in Catalysis, Volume 3Edited by Bing Zhou, Scott Han, RobertRaja, and GaborA. Somorjai
Controlled Synthesis of Nanoparticles in Microheterogeneous SystemsVincenzo Turco Liveri
Nanoscale Assembly TechniquesEdited by Wilhelm T.S. Huck
OrderedPorous Nanostructures and ApplicationsEdited by Ralf B. Wehrspohn
SurfaceEffects in Magnetic NanoparticlesDino Fiorani
Alternative Lithography: Unleashing the Potentials of NanotechnologyEdited by Clivia M. Sotomayor Torres
Interfacial Nanochemistry: Molecular Scienceand Engineeringat Liquid-Liquid InterfacesEdited by Hitoshi Watarai
Nanoparticles: Building Blocks for NanotechnologyEdited by Vincent Rotello
Nanostructured CatalystsEdited by SusannahL. Scott, Cathleen M. Crudden, and ChristopherW. Jones
Self-Assembled Nanostructureslin Z. Zhang, Zhong-lin Wang, Jun Liu, Shaowei Chen, and Gang-yu Liu
Semiconductor Nanocrystals: From BasicPrinciples to ApplicationsEdited by AlexanderL. Efros, DavidJ. Lockwood, and Leonid Tsybeskov
Sudipta SealEditor
Functional NanostructuresProcessing, Characterization,and Applications
~ Springer
EditorSudiptaSealAdvanced Materials Processing and Analysis CenterUniversity of Central Florida4000 Central FloridaBlvd.Orlando. Florida32816-2455
ISBN: 978-0-387-35463-7 e-ISBN: 978-0-387-48805-9
Library of Congress Control Number: 2007943481
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Tomy wifeShantaanddaughter AnouskaMy parents: father Prof. Bijoyand mother MaryMy brotherand his wife: Pradipta and Gayatri
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Contents
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
1. Advanced Ceramics and Nanocomposites ofHalf-metallic Ferromagnetic CrOz for Magnetic,GMR and Optical Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
S. Ram, S. Biswas, and H. I-Fecht
1. Introduction 11.1. Definition of Half-metals and Half-metallic Compounds . . . . 11.2. Spin Polarization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Chromium Dioxide Ceramics and Nanocomposites 62.1. Crystal Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2. Methods of Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Stability and Controlled Transformation-in Phase-stabilizedParticles 21
4. Electronic Band Structure 245. Electronic Properties 27
5.1. Dielectric Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.2. Electrical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6. Magnetic Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377. GMR Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428. Optical Properties 489. Applications . .. . . . .. . . . ... . . . . . . . ... . . .. . . . . ... . .. . ... . 52
10. Toxicities and Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Acknowledgment 53References 53Questions 63
2. Functional Nanostructured Thin Films. . . . . . . . . . . . . . . . . . . . . 65
Hare Krishna and Ramki Kalyanaraman
1. Introduction 65
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1.1. Fabricating Nanostructured Surfaces . . . . . . . . . . . . . . . . . . . 671.2. Self-assembly of Nanostructures by Film Nucleation
and Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 691.3. Self-assembly by Ion Irradiation. . . . . . . . . . . . . . . . . . . . . . . 771.4. Characterization.. . ............. . .... . . . . .. . . . . . . . . 811.5. Applications. . ... . .. . . . .. . . . . . . . .. . . . . . . . . . . . . .... 931.6. Conclusion..... ....... .... ..... . . . . . . .. . . . . . . . . . . . 100
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101References 101Questions 106
3. MEMS for Nanotechnology: Top-down Perspective.......... 107
Ghanashyam Lande, Arum Han, Hyaung J. Cho
1. Introduction ... . .. . . . . . .. . .. . . . .. . ... . . . ... . . ... ....... 1072. Micromachining Techniques 108
2.1. Photolithography.. .. . .. . . . . . . . . . . . .. . . . ... . . .. . .. . . 1082.2. Bulk Micromachining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1102.3. Surface Micromachining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1132.4. Combined Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 115
3. Nanofabrication... . ............. ... . . . ... . . . . . . . . . . . . . . 1173.1. Electron Beam Lithography (EBL) . . . . . . . . . . . . . . . . . . . . . 1193.2. Scanning Probe Lithography (SPL) . . . . . . . . . . . . . . . . . . . . 1243.3. Soft Lithography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263.4. Nanoimprint Lithography (NIL) . . . . . . . . . . . . . . . . . . . . . .. 128
4. Integration and Interface 1314.1. Carbon Nanotube (CNT) Manipulation-with
Microelectrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1314.2. Nanoparticle Interface with Microelectrode . . . . . . . . . . . . . . 132
5. Applications .. . . . . . .. . ... . ... . ... . ... . ... . ... . . .. .... . . 1345.1. Nanobeam ... . .... . . ... . . ... . . .. . . . . . .. . . . . . . . . . . . 1345.2. Nanoprobe.................... ... . .... ... . ... . ... . 1385.3. Nanopore and Nanogap . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1415.4. Channel and Needle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1435.5. Nanowire and Nanotube . . . .. . . . . . . .. . . . . . . . . . . . . . . . . 1475.6. Nanocrystal and Nanocrescent . . . . . . . . . . . . . . . . . . . . . . . . 1545.7. Tools for Nanoscale Manipulation. . . . . . . . . . . . . . . . . . . . . 155
6. Conclusion .. . . . . . . ... . .. . . .. . . ... . ... . ... ....... .... . . 158Acknowledgment 160References 160Questions 167
Contents ix
4. Nanostructured Biomaterials... .......... . ..... ........... 168
SamarJ. Kalita
I. Introduction 1681.1. Biocompatibility and Types of Tissue Responses. . . . . . . . . . . 172
2. Classification 1732.1. Metallic Biomaterial s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1732.2. Ceramic Biomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1812.3. Polymeric Biomaterials 1962.4. Composite Biomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 202
3. Cell Response to Nanobiomaterials and Current Advances 2044. Summary 208References 210Questions 219
5. Self-Assembly in Nanophase Separated Polymerand Thin Film: Supramolecular Assembly. . . . . . . . . . . . . . . . . . 220
Naba K. Dutta and Namita Roy Choudhury
1. Introduction 2201.1. Self-assembly................ ... . ... .. ...... ....... 2201.2. Strategies of Self-assembling Supramolecular
Complexes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2232. Mesophase Separation in Block Co-Polymer System . . . . . . . . . . .. 228
2.1. Evolution of Supramolecular Assembly inBlock Copolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
2.2. Synthetic Strategy of Multiblock Copolymers . . . . . . . . . . . . . 2402.3. Nanophase Separation in Side Chain Crystalline
Polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2483. Self-Assembled Nanoparticle System . . . . . . . . . . . . . . . . . . . . . . .. 253
3.1. Zero-dimensional Self-assembly . . . . . . . . . . . . . . . . . . . . . . . . 2533.2. Nanoparticles in Nanostructured Polymer . . . . . . . . . . . . . . . . 2583.3. Two-dimensional Thin Film. . . . . . . . . . . . . . . . . . . . . . . . . . . 2613.4. Self-assembly in Biocompatible System
and Biomolecular Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . 2703.5. Supramolecular Assembly via Hydrogen Bonding. . . . . . . . .. 2723.6. Molecular Clusters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
4. Characterization of a Self-assembled System 2774.1. Advanced Scattering Techniques 2784.2. Advanced Surface Analysis Techniques . . . . . . . . . . . . . . . . .. 2824.3. MALDI-MS. TOF-SIMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
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4.4. Microscopic Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2844.5. Solid-state NMR in Characterizing Self-assembled
Nanostructures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2864.6 . Advanced Thermal Analysis. . . . . . . . . . . . . . . . . . . . . . . . . .. 287
5. Application and Future Outlook 2896. Acknowledgment . . . . . . .. . . . .... ... ...... .... . . .. . ... . ... 291References 291Questions 304
6. Nanostructures: Sensor and Catalytic Properties. . . . . . . . . . . . 305
B. Roldan Cuenya, A. Kolmakov
1. Introduction 3051.1. Overview .. ... .... .. .... . ... . . . .. .. . .... ... .... . ... 3051.2. Why are Nanostructures Important for Gas Sensing
and Catalysis? (Structure-Sensitivity Relationship) . . . . . . . . . 3071.3. The Impact on the Fundamental Science . . . . . . . . . . . . . . . . . 309
2. Phenomena at Nanoscaled Metal and Semiconducting OxideSurfaces Relevant to Gas Sensing and Catalysis . . . . . . . . . . . . . . . . 3092.1. Pristine Oxide Surfaces : Physisorption vs. Chemisorption . . . . 3092.2. Band Bending and Charge Depletion . . . . . . . . . . . . . . . . . . . . 3112.3. Chemisorption and Magnetization. . . . . . . . . . . . . . . . . . . . . . 313
3. Nanostructured Gas Sensors: Some Examples of DetectionPrinciples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3153.1. Two-dimensional Nanoscaled Metal/Oxide/Semiconductor
Diodes.. . . . . . . . . 3153.2. Quasi-ID Nanostructured Oxides as a New Platform
for Gas Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3234. New Surface Science Trends for the Characterization
of Nanostructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3315. Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 334Acknowledgment 335References 335Question s 344
7. Nanostructured High-Anisotropy Materials forHigh-Density Magnetic Recording. . . . . . . . . . . . . . . . . . . . . . . . . . 345
J. S. Chen, C. f. Sun, G. M. Chow
I . Introduction 3452. Definition and Characterization of Chemical Ordering of
L10 FePt 349
Contents xi
2.1. Chemical Ordering of Llo FePt . . . . . . . . . . . . . . . . . . . . . . . . 3492.2. Characterization ofLlo FePt Chemical Ordering . . . . . . . . . . 351
3. Preparation of Llo FePt Films and Parameters Affectingthe Chemical Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3563.1. Preparation ofL1 0 FePt Films. 3563.2. Effects of Temperature, Stoichiometry and Film Thickness
on Chemical Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3563.3. Promotion of Chemical Ordering by Doping . . . . . . . . . . . . . . 3583.4. Strain- or Stress-Induced Llo Ordering. . . . . . . . . . . . . . . . . . 3603.5. Other Approaches to Enhance Llo Ordering . . . . . . . . . . . . . . 368
4. Intrinsic Properties of the Ll 0 FePt Films . . . . . . . . . . . . . . . . . . . . . 3694.1. Magnetocrystalline Anisotropy, Magnetization and
Curie Temeperture of Ll o FePt Films. . . . . . . . . . . . . . . . . . . . 3694.2. Effects of Size and Interface on Coercivity and
Magnetization Reversal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3745. Application ofLlo FePt alloy thin film for perpendicular
magnetic recording 3785.1. Control of FePt (DOl) Texture . . . . . . . . . . . . . . . . . . . .. . . . . . 3795.2. Control of Exchange Coupling and Grain Size
of FePt Films. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3865.3. Recording Performance of Ll o FePt Perpendicular Media. . .. 398
6. Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 405References 405
8. High-Resolution Transmission Electron Microscopyfor Nanocharacterization . .. . . . . .. . .• . . .. . . . .. •. .. . . . . . . . . 414
Helge Heinrich
1. Introduction 4142. Sample Preparation 416
2.1. Electropolishing . .. . . . . . .. . .. . . . . . . . . . . .. . . .. . .... .. 4182.2. Ion-beam Milling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4192.3. The Focused Ion-beam Technique. . . . . . . . . .. . . . . . . . . . . . 4192.4. Tripod Polishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4212.5. Powders and Suspensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
3. Principles of Image Formation 4233.1. The Transmission Electron Microscope . . . . . . . . . . . . . . . . .. 4243.2. The Ewald Construction and the Reciprocal Space. . . . . . . . . 4333.3. Scattering Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 452
4. Imaging of Nanostructured Material 4584.1. High-resolution Transmission Electron Microscopy
(HRTEM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 458
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4.2. Scanning Transmission Electron Microscopy. . . . . . . . . . . . . . 4704.3. Electron Holography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477
5. Analytical Electron Microscopy 4825.1. Electron Energy-loss Spectroscopy. . . . . . . . . . . . . . . . . . . . .. 4855.2. Energy-filtered Electron Microscopy. . . . . . . . . . . . . . . . . . .. 4885.3. X-ray Analysis and Chemical Mapping. . . . . . . . . . . . . . . . . . 490
6. New Developments in Electron Microscopy . . . . . . . . . . . . . . . . . .. 4937. Acknowledgments 494References 494Questions 500Solutions to Questions 502
9. Applications of Atomic Force Microscope (AFM)in the Field of Nanomaterials and Nanocomposites . . . . . . . . . 504
S. Bandyopadhyay, S. K. Samudrala, A . K. Bhowmick,and S. K. Gupta
1. Introduction 5041.1. Nanomaterials . . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . . . . . . . 5051.2. Nanocomposites...... ............ .. . ... .... . ... . ... 5081.3. Characterization Techniques. . . . . . . . . . . . . . . . . . . . . . . . . .. 509
2. Atomic Force Microscope Instrumentation and Setup 5122.1. Principle of Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5132.2. Factors that Influence the Precision and Accuracy
of AFM Imaging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5152.3. Different Modes ofImaging in AFM . . . . . . . . . . . . . . . . . . . . 5172.4. Constant Force and Constant Height Criterion. . . . . . . . . . . . . 5202.5. AFM in Nanotechnological Applications . . . . . . . . . . . . . . . . . 520
3. Contributions of AFM to the Field of Nanotechnology 5213.1. Characterization of NanoparticleslNanomaterials . . . . . . . . . . 5213.2. Characterization of Nanocomposites . . . . . . . . . . . . . . . . . . . . 5263.3. Conductive AFM as a Means to Characterize
Electrical Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5383.4. Characterization of Nano-Mechanical and
Nano-Tribological Properties . . . . . . . . . . . . . . . . . . . . . . . . .. 5403.5. NanofabricationlNanolithography . .. . . . . . . . . .. . . . .. . .. . . 550
4. Concluding Remarks 557Acknowledgments 557References 558Questions 568
Index........... .. .. ... ........ ...... ..... ... ... ........... 569
Preface
Functional nanostructures are materials considered to work at the molecular levelcomprised of nanometer scale components arranged in three-dimensions. Thesematerials can be in the form of nanofilms, nanotubes, nanodots or nanowires, whosespatial arrangement and other attributes like size and shape can lead to variousapplications. While synthesis and fabrication of these nanostructures are always achallenge, however, tailoring these nanostructures can find applications biology,materials science, gas sensors, potential memory storage devices, surface plasmonwaveguides, nanocatalysts, spatially ordered metal nanocatalyst seeds for highefficiency flat-panel displays from carbon-nanotube arrays. Control fabrication toachieve unique spatial arrangement of the nanofeatures, control of its size, shape,composition, and crystallographic orientation is important and can be achievedby various synthesis routes. This book describes some of the aspects of functionalnanostructures, from fabrication , characterization to novel applications for the 2151
century nanotechnology boom.The article by Ram et al., is primarily focused on the understanding of syn
thesis, fabrication, and control of the electronic structure and derived magnetic ,GMR, and optical properties of a specific class of ferromagnetic ceramics andhybrid composites in forms of films, nanowires, and fine powders . Such materials,also called "half-metallic compounds" represent a new generation of spintronics,photonics , kinds of sensors, and nonlinear optical devices. In such systems , theelectrical conduction is carried out exclusively by charge carriers of one spin direction, i.e., the conduction electrons are "-'100% spin polarized . This distinctiveproperty of spin polarization of charge carriers in such materials makes them themost appropriate to be utilized not only in magnetic tunnel junctions and spinpolarizers for current injection into semiconductors, which are the constituentcomponents of non-volatile magnetic random access memories and other spindependent devices, but also to increase the efficiency of optoelectronic devicesand even in self-assembled quantum computers.Typical magnetic , GMR, optical,and other properties are reviewed and presented with identified mechanisms andmodels on case to case basis with selective examples . Finally, toxicities and hazards, which may be encountered during processing or handling such materials, arepointed out.
xiii
xiv Preface
In the 2nd chapter, various processing techniques to create nanostructuresare reviewed with an emphasison self-assembly approaches. This section furtherdiscusses two important computer image analysis techniques that are importantfor characterization of nanoscale features like spatialorder (Fourieranalysis)andmorphology (Minkowski analysis). The chapterconcludeswithexamples of someimportant applications requiring ordered surface nanostructures.
The 3rd chapter deals with MEMS research, that has started from siliconmicrofabrication, emergedas novel methodology for the miniaturization and integrationofsensorsandactuators, andstartedproviding top-down,cross-disciplinarysolutionsto nanoscale fabrication and characterization. The implementations andapplications of those were found in the sensors and actuators using nanoparticles, nanobeams, nanoprobes, nanopores, nanogaps, nanochannels, nanotubes andnanowires are discussed.
A recent trend is shifting towards nanotechnology lookingfor improvementin the biological responses and overall life of medical implants, made of novelbiomedical materials called 'biomaterials' is presented in Chapter 4. Designingof biomaterials at the nano scale level is critical for control of cell-biomaterialsinteractions, which can be used beneficially in developing implants with desiredcharacteristic properties. Biological cells have dimensions within the range of1-10 urn and contain many examples of extremely complex nano-assemblies;including molecularmotors, which are complexes embedded within membranesthatare powered by naturalbiochemical processes. Various examples of nanoscalestructures, nano motorsand nanosystemsare present in abundance and in vivo indifferent biological systems. This chapter presents some of the current advancesin the development of nanostructured metallic, ceramic, polymeric and compositebiomaterials. In addition, the chapter also discusses various types of traditionalbiomaterials with their properties and applications to help new scholars in thisfield to gather solid background knowledge on biomaterials, without having torefer to other texts.
Chapter 5 describes self-assembly processes in polymeric systems. Selfassembly (SA) involves recognition or bindingprocesses and the individual componentcontainsenoughinformation to recognize and interactwithotherappropriate unit to build a template for a structurecomposed of multiple units. The mostwidely studiedaspectof self-assembly is molecularself-assembly and the molecular structure determines the structure of the assembly. Molecular self-assemblyis also ubiquitous in chemistry and material science, the formation of molecularcrystals, liquidcrystals,semicrystalline polymers, colloids,phase separatedpolymers,andself-assembled monolayers are uniqueexamples, whichare reviewed indetail in this chapter.
Chapter6 provides someexamples of newexperimental trendsin the fields ofcatalysisandchemicalsensing. In particular, sensorsbasedon chemically-inducedelectronicphenomena on nanometer-scale metal films deposited on semiconductor junctions (MS and MOS devices), quasi-ID oxide chemiresistors and cherniPETdevicesandchemically-tunablemagnetic nanostructures havebeendiscussed.
Preface xv
It has been shown, that nanometer-thick MS and MOS devices can be used as highlyselective gas sensors. The main limitation of these devices is that they require lowtemperature (l25-200 K) operation in order to minimize thermal noise. After lessthan a decade of development, chemiresistors and chemi-FET nanosensors madeof quasi-ID oxides have demonstrated superior performance over conventionalbulk-sensors and are currently considered the most promising sensing elementsfor the next generation of solid state gas sensors. There are still plenty of unexplored lines of fundamental research , particularly in the size range where quantumconfinement dominates the electron ic structure of nano-objects , which is reviewedherein. Furthermore, there exists a strong necessity of further developing new spectroscopic and nondestructive microscopic techniques to probe surface propertie sof individual nanostructures, in particular, the ones that can be operated underrealistic sensing conditions. A brief overview is presented in this section.
Chapter 7 presents a brief review of the demand for the development ofdata storage technology to provide storage media with increased storage density.To achieve high density a reduction in the grain size is required so as to enablemore grains per unit area on the magnetic media. In this chapter, the structuralcharacterization and some intrinsic properties of LloFePt such as the origin of highanisotropy and finite size and interface effects were reviewed. However, practicalapplications of FePt films as recording media face many technical challengesincluding desirable reduction of ordering temperature, control of the FePt (001)texture and decrease of media noise. Therefore, more efforts were made to reviewthe current status on solving above problems.
While processing and properties are important in nanostructures, detailedcharacterization is needed to understand the science behind nanstructures. Properties of nanoscaled materials are influenced by the size, distribution and orientation of objects, but they also depend on the internal structures and chemistriesof these individual particles , precipitates or domains. Environmental effects liketemperature, mechanical stresses , radiation damage and corrosion may reduce thelong-term stability of devices or materials based on nanomaterial s. Next two sections in the book deals with Transmission Electron Microscopy and Atomic ForceMicroscopy, one of the few essential analytical tools in nanocharacterization.
Chapter 8 reviews the role of Transmission electron microscopy for the studyof internal structures requires special sample preparation, while scanning probetechniques and scanning electron microscopy for surface characterization are essentially non-destructive techniques. The most important transmission electronmicroscopy methods for nanomaterials are reviewed. Bright-field and dark-fieldimaging is employed for the analysis of the sizes and distribution of particles andfor the identification of structural defects. High-resolution micrographs yield valuable data on interfaces and defects in crystallites. Diffraction techniques are used toidentify local crystal structures. Analytical methods like energy dispersive X-rayanalysis and electron energy-loss spectroscopy as well as high-angle annular darkfield scanning transmission electron microscopy and holography are importanttools in qualitative and quantitati ve studies of the local chemistry. Transmission
xvi Preface
electronmicroscopy isemployedfor feedbackon processingof nanomaterials andhelps in the identification of methods to improve reliability and reproducibilityof the nanomaterials properties. New developments in electron optics soon becomeavailable to an extendedrangeof usersare discussed. The prospectsof theseimproved analytical methods for research on nanostructures are outlined.
It is well known basedon the research in the field of nanotechnology that thefull exploitation of fundamental characteristics of nano-reinforcements and developmentof nanostructures wouldfacilitate the achievement of enhancedproperties(for example, physical, mechanical, optical, magnetic, electric, and rheologicalproperties) in these materials. So, an accuratecharacterization of these materialsat an atomiclevel is neededthat requires a preciseunderstanding and measurementof the surface and interfacial phenomena along with the other factors like size ofthe nanoparticles, dispersion, crystallinity, and so forth. Despite the availability ofdifferentadvanced characterization techniques forthesepurposes, AFMprovides abetteralternative due to the fact that it can be operatedin mostof the environmentswith excellentresolution, provides three-dimensional qualitative and quantitativeinformation, and also used to characterize nano-mechanical and nanotribologicalproperties of different materials. In this chapter 9, the authors review the recentprogress and the fundamental aspects on the application of AFM to characterizenanomaterials and nanocomposites.
