Nanocharacterisation (Nanoscience & Nanotechnology) - Hardcover

Hardcover

ISBN 10: 0854042415 ISBN 13: 9780854042418

Verlag: Royal Society of Chemistry, 2007

Inhaltsangabe

Chemical characterisation techniques have been essential tools in underpinning the explosion in nanotechnology in recent years and nanocharacterisation is a rapidly developing field. Contributions in this book from leading teams across the globe provide an overview of the different microscopic techniques now in regular use for the characterisation of nanostructures. Essentially a handbook to all working in the field this indispensable resource provides a survey of microscopy based techniques with experimental procedures and extensive examples of state of the art characterisation methods including, Transmission Electron Microscopy, Electron Tomography, Tunneling Microscopy, Electron Holography, Electron Energy Loss Spectroscopy This timely publication will appeal to academics, professionals and anyone working fields related to the research and development of nanocharacterisation and nanotechnology.

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Über die Autorin bzw. den Autor

A I Kirkland is Professor of Materials at Oxford University and the author of over 170 refereed papers. He was awarded "best materials paper" of 2005 by the Microscopy Society of America. Since 2000 he has also been involved in the characterisation of CCD cameras for TEM. His most recent work involves the development of approaches to complex phase extension and diffractive imaging to further improve resolution. J Hutchinson is a Reader in Materials at Oxford University and has published over 300 refereed papers during his career.. He is currently Vice-President of the Royal Microscopical Society (President 2002-2004), and from 2000-2004 was also a member of the Executive Board of the European Microscopy Society. He has also been involved in the development of the world's first double-aberration-corrected electron microscope.

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Chemical characterisation techniques have been essential tools in underpinning the explosion in nanotechnology in recent years and nanochaterisation is a rapidly developing field. Contributions in this book from leading teams across the globe provide an overview of the different microscopic techniques now in regular use for the characterisation of nanostructures. Essentially a handbook to all working in the field this indispensable resource provides a survey of microscopy based techniques with experimental procedures and extensive examples of state of the art characterisation methods including: Transmission Electron Microscopy, Electron Tomography, Tunneling Microscopy, Electron Hologrpahy, Electron Energy Loss Spectroscopy. This timely publication will appeal to academics, professionals and anyone working fields related to the research and development of nanocharacterisation and nanotechnology. The Editors A I Kirkland is Professor of Materials at Oxford University and the author of over 170 refereed papers. He was awarded ""best materials paper"" of 2005 by the Microscopy Society of America. Since 2000 he has also been involved in the characterisation of CCD cameras for TEM. His most recent work involves the development of approaches to complex phase extension and diffractive imaging to further improve resolution. J l Hutchinson is a Reader in Materials at Oxford University and has published over 300 refereed papers during his career.. He is currently Vice-President of the Royal Microscopical Society (President 2002-2004), and from 2000-2004 was also a member of the Executive Board of the European Microscopy Society. He has also been involved in the development of the world's first double-aberration-corrected electron microscope.

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Nanocharacterisation

By Augus I Kirkland, John L Hutchison

The Royal Society of Chemistry

Copyright © 2007 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-0-85404-241-8

Contents

Chapter 1 Characterisation of Nanomaterials Using Transmission Electron Microscopy D. J. Smith, 
Chapter 2 Scanning Transmission Electron Microscopy A. R. Lupini, S. N. Rashkeev, M. Varela, A. Y. Borisevich, M. P. Oxley, K. van Benthem, Y. Peng, N. de Jonge, G. M. Veith, S. T. Pantelides, M. F. Chisholm and S. J. Pennycook, 
Chapter 3 Scanning Tunneling Microscopy of Surfaces and Nanostructures M. R. Castell, 
Chapter 4 Electron Energy-loss Spectroscopy and Energy Dispersive X-Ray Analysis R. Brydson, 
Chapter 5 Electron Holography of Nanostructured Materials R. E. Dunin-Borkowski, T. Kasama and R. J. Harrison, 
Chapter 6 Electron Tomography M. Weyland and P. A. Midgley, 
Chapter 7 In-situ Environmental Transmission Electron Microscopy P. L. Gai, 
Subject Index, 291, 

CHAPTER 1

Characterisation of Nanomaterials Using Transmission Electron Microscopy

D. J. SMITH

Department of Physics, Arizona State University, Tempe, AZ 85287 USA

1.1 Introduction

The Transmission Electron Microscope (TEM) has evolved over many years into a highly sophisticated instrument that has found widespread application across the scientific disciplines. Because the TEM has an unparalleled ability to provide structural and chemical information over a range of length scales down to the level of atomic dimensions, it has developed into an indispensable tool for scientists who are interested in understanding the properties of nanostructured materials and in manipulating their behaviour.

The resolution of the optical microscope is restricted by the wavelength of visible light, which thus precludes atomic-scale imaging. In contrast, an energetic electron has a wavelength of much less than 1 Å (where 1 Å = 10-10 m), so that an enormous improvement in resolution can be achieved, at least in principle, by using a beam of fast electrons for imaging. A suitable combination of (magnetic) electron lenses is required, both for focusing the electron beam onto the object and also for providing an enlarged image. Maximum magnifications at the microscope are typically close to or exceed one million times, so that details of the nanoscale object are clearly visible on the final viewing screen or recording medium.

Image formation in the TEM is more complicated in practice than is the case for the optical microscope. Strong magnetic fields are needed for focusing the electron beam, and these cause electrons to take a spiral trajectory through the lens field. In addition, a major restriction on ultimate microscope performance results from unavoidable aberrations of round electron lenses. Primarily, due to the need for a compromise between small-angle diffraction effects and wide-angle spherical-aberration limits, the resolution, d can be roughly expressed by an equation of the form

d = A C1/4sλ3/4 (1.1)

where CS is the spherical aberration coefficient of the objective lens, λ is the electron wavelength, and A is a constant with a value ranging from 0.43 to 0.7 depending on the type of imaging (coherent, incoherent, or phase contrast). Values of d typically range from about 3.0 Å down to 1.0 Å as electron energies are increased from 100 to 1250 keV. Modern-day TEMs operating at 200 or 300 keV have resolution limits well below 2.0 Å, which is comparable to the spacing between atoms. Individual columns of atoms can thus be resolved in crystalline materials, which must first, however, be oriented so that the incident electron beam is aligned along some major crystallographic zone axis of the sample.

The power of the technique is illustrated by the example in Figure 1.1, which shows the boundary region between two Al crystals, both of which are oriented so that the electron beam is parallel with the [001]-type zone axis. Each black spot in the image marks the position of a column of Al metal atoms viewed in an end-on geometry. It is obviously straightforward to visualise the periodic array of misfit dislocations (arrowed) that accommodate the angular misfit of 6° 1 between the two crystals, and further analysis would enable the detailed atomic structure around the dislocation core to be determined.

This chapter begins by providing a brief introduction to the TEM and some of the key aspects of high-resolution imaging. Applications to nanostructured materials are then described in greater detail, and some emerging trends and unresolved issues are briefly discussed. For further information about microscope operation and more details about applications to a broader range of materials, the interested reader is referred to the review articles and monographs listed at the end of the chapter.

1.2 Imaging

1.2.1 Transmission Electron Microscopy

In the standard TEM operating mode, which is commonly referred to as amplitude or diffraction contrast imaging, only a fraction of those electrons that have passed through the sample are used to form the highly magnified final image. Most of the scattered (or diffracted) electrons are prevented from reaching the image plane by positioning a small objective aperture located in the back focal plane of the objective lens. This aperture thus serves to determine the image contrast. For the case of crystalline samples, the electron diffraction pattern (EDP) is used to ensure that the orientation of the specimen relative to the direction of the incident electron beam will satisfy a strongly diffracting condition. Many common structural defects have a highly characteristic appearance under such diffraction contrast conditions. The spacings and angles between crystal lattice planes can also be determined if the EDP is first calibrated using a known material. In addition, the availability of a crystalline substrate or support can provide a convenient method for sample orientation during observation. By using the substrate EDP for reference purposes, internal interfaces can be aligned perpendicular to the electron-beam direction so that any changes in the microstructure of thin films and multilayers can then be determined as a function of film thickness. As an example, Figure 1.2 shows a multilayered Magnetic Tunneling Transistor (MTT) deposited directly on the native oxide of a Si substrate. The individual layers of the MTT can be clearly recognised, and their thickness uniformity is easily confirmed. Finally, it should be appreciated by the reader that examination of such complex samples with the TEM can represent a serious challenge to the electron microscopist. Because of considerable differences in thinning rates, it will often be difficult to prepare samples that are electron transparent across the entire region of interest simultaneously. Descriptions of different approaches for preparing electron-transparent specimens can be found elsewhere.

1.2.2 High-Resolution Electron Microscopy

In the technique of High-Resolution Electron Microscopy (HREM), a much larger objective aperture (or sometimes none at all) is used. The directly transmitted beam can then interfere with one or more diffracted beams, and the contrast across the image will depend on the relative phases of the various beams. This imaging mode is thus often referred to as phase contrast imaging. When the microscope imaging conditions are properly adjusted (lens defocus, image astigmatism,...

Details zur Ausgabe

• Verlag: Royal Society of Chemistry
• Erscheinungsdatum: 2007
• Sprache: Englisch
• ISBN 10: 0854042415
• ISBN 13: 9780854042418
• Einband: Gebundene Ausgabe
• Anzahl der Seiten: 304
• Herausgeber: Kirkland Augus I., Hutchison John L.
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: preigu; mail@preigu.de; ; Lengericher Landstr. 19; Osnabrück; 49078; Deutschland