Surface and Interface Characterization by Electron Optical Methods PDF
Preview Surface and Interface Characterization by Electron Optical Methods
Su rface and Interface Characterization by Electron Optical Methods NATO ASI Series Advanced Science Institutes Series A series presenting the results of activities sponsored by the NATO Science Committee, which aims at the dissemination of advanced scientific and technological knowledge, with a view to strengthening links between scientific communities. The series is published by an international board of publishers in conjunction with the NATO Scientific Affairs Division A Life Sciences Plenum Publishing Corporation B Physics New York and London C Mathematical Kluwer Academic Publishers and Physical Sciences Dordrecht, Boston, and London o Behavioral and Social Sciences E Applied Sciences F Computer and Systems Sciences Springer· Verlag G Ecological Sciences Berlin, Heidelberg, New York, London, H Cell Biology Paris, and Tokyo Recent Volumes in this Series Volume 184-Narrow-Band Phenomena-Influence of Electrons with Both Band and Localized Character edited by J. C. Fuggle, G. A. Sawatzky, and J. W. A"en Volume 185-Nonperturbative Quantum Field Theory edited by G. 't Hooft, A. Jaffe, G. Mack, P. K. Mitter, and R. Stora Volume 186-Simple Molecular Systems at Very High Density edited by A. Pol ian, P. Loubeyre, and N. Boccara Volume 187-X-Ray Spectroscopy in Atomic and Solid State Physics edited by J. Gomes Ferreira and M. Teresa Ramos Volume 188-Reflection High-Energy Electron Diffraction and Reflection Electron Imaging of Surfaces edited by P. K. Larsen and P. J. Dobson Volume 189-Band Structure Engineering in Semiconductor Microstructures edited by R. A. Abram and M. Jaros Volume 190-Squeezed and Nonclassical Light edited by P. Tombesi and E. R. Pike Volume 191-Surface and Interface Characterization by Electron Optical Methods edited by A. Howie and U. Valdre Series B: Physics Surface and Interface Characterization by Electron Optical Methods Edited by A. Howie University of Cambridge Cambridge, United Kingdom and U. Valdre University of Bologna Bologna, Italy Plenum Press New York and London Published in cooperation with NATO Scientific Affairs Division Proceedings of a NATO Advanced Study Institute on the Study of Surfaces and Interfaces by Electron Optical Techniques held April 4-15,1987, in Erice, Sicily, Italy Library of Congress Cataloging in Publication Data NATO Advanced Study Institute on the Study of Surfaces and Interfaces by Elec- tron Optical Techniques (1987: Erice, Italy) Surface and interface characterization by electron optical methods I edited by A. Howie and U. Valdre. p. cm.-(NATO ASI series. Series B, Physics; v. 191) "Proceedings of a NATO Advanced Study Institute on the Study of Surfaces and Interfaces by Electron Optical Techniques, held April 4-15, 1987, in Erice, Sicily, Italy"-CIP t.p. verso. Bibliography: p. Includes index. 1. Surfaces (Physics)-Technique-Congresses. 2. Electron microscopy- Congresses. 3. Electron microscope, Transmission-Congresses. I. Howie, A. II. Valdre, U. (Ugo). III. Title. IV. Series. QC173.4.S94N385 1987 88-28989 530.4'1-dc19 CIP © 1988 Plenum Press, New York Softcover reprint ofthe hardcover I st edition 1988 A Division of Plenum Publishing Corporation 233 Spring Street, New York, N.Y. 10013 All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher ISBN 978-1-4615-9539-7 ISBN 978-1-4615-9537-3 (eBook) DOl 10.1007/978-1-4615-9537-3 STM image of the 7 x 7 reconstruction at the Si (111) surface. The distance between the main 6-fold symmetry centers is 2.6 nm. Color enhancement of the intensity scale reveals fine details of atomic heights and bonding states at the surface. A surface step is visible as a discontinuity running vertically near the center of the figure. Atoms are blue. Colors from blue to red indicate details further away from the surface. (Courtesy Drs. J . E. Demuth, R. J . Hamers, R. M. Tromp, and M. E. Weiland. Fig. 3 from chapter by Garcia.) a b I I Magnetic domain images from an Fe (100) surface, measured simultaneously for the spin polarization vector component along the horizontal axis (a) and the vertical axis (b). Areas of the same color have the same magnetization (see arrows). Within the gray areas in (a) and (b) the horizontal (a) and vertical (b) polarization components, respectively, are zero, while the ver- tical and horizontal components are maximum. The scale markers each correspond to 60 I-'m (Fig. 2 from chapter by Kirschner.) PREFACE The importance of real space imaging and spatially-resolved spectroscopy in many of the most significant problems of surface and interface behaviour is almost self evident. To join the expertise of the tradi tional surface scientist with that of the electron microscopist has however been a slow and difficult process. In the past few years remarkable progress has been achieved, including the development of new techniques of scanning transmission and reflection imaging as well as low energy microscopy, all carried out in greatly improved vacuum conditions. Most astonishing of all has been the advent of the scanning tunneling electron microscope providing atomic resolution in a manner readily compatible with most surface science diagnostic procedures. The problem of beam damage, though often serious, is increasingly well understood so that we can assess the reliability and usefulness of the results which can now be obtained in catalysis studies and a wide range of surface science applications. These new developments and many others in more established surface techniques are all described in this book, based on lectures given at a NATO Advanced Study Institute held in Erice, Sicily, at Easter 1987. It is regretted that a few lectures on low energy electron diffraction and channeling effects could not be included. Fifteen lecturers from seven different Countries and 67 students from 23 Countries and a wide variety of backgrounds attended the school. Substantial problem-solving sessions and computer demonstrations were arranged to back up the lectures and a number of these problems have been reproduced in the book. We wish to thank all the lecturers for their effort and patience in producing the material for the book. For permission to include various figures and quotations (specifically identified where appropriate in the text) we are grateful to the American Institute of Physics, the American Physical Society, the International Business Machines Corporation and the Nobel Foundation. The two enthralling lectures given enthusiastically by Dr Wolfgang Telieps were a high point of the School. It was thus with great shock and sorrow that we learnt of his death so soon afterwards. We are grateful to his colleague, Professor Bauer, for providing the obituary notice included here and for completing the write up of the relevant lecture notes. The success of the School was greatly assisted by a contribution from NATO and from the facilities of the Ettore Majorana Centre for Scientific Culture. For secretarial support we are grateful to Mrs Irene Salerno, Mrs Mary Waterworth and Miss Vanna Valdre. A. Howie and U. Valdre June 1988 v OBITUARY Wolfgang Telieps, who gave one of the most interesting lectures in this school, died in a tragic car accident on May 31, 1987 at the age of 36. He had studied physics at the Technical University Clausthal, where he received a M.S. degree in physics in 1977 and his Ph.D. in 1983. For his M.S. thesis work he studied the imaging column of the low energy electron microscope; in his Ph.D. project he took over the responsibility for the complete instrument . In spite of strong discouragement by referees, he succeeded in demonstrating the viability of LEEM . This achievement and the work which he did in the following years in the course of his preparation for the "habilitation" rapidly brought him international recognition. Wolfgang Telieps was not only an outstanding physicist but also a great human being who was liked by all who knew him for his pleasant personality, his objectiveness, his tolerance, his willingness to help and many other positive characteristics which made him an ideal collaborator. His untimely death has thus robbed, not only the scientific community of a very talented young member, but also his colleagues of an unforgettable friend. vi CONTENTS Principles and techniques of transmission imaging of surfaces . . . . . A. Howie Catalyst studies by scanning transmission electron microscopy 11 A. Howie Localised surface imaging and spectroscopy in the scanning transmission electron microscope . . .. ..... 19 A. Howie Fundamentals of high resolution transmission electron microscopy. 31 D.J. Smith Profile imaging of small particles, extended surfaces and dynamic surface phenomena. . . . . . . . . . . . . . .. .... 43 D.J. Smith Transmission electron microscopy and diffraction from semiconductor interfaces and surfaces. . . . . . . . . . . . . . . . . . . . 55 J.M. Gibson The transmission electron microscopy of interfaces and multilayers. .. 77 W.M. Stobbs Surface microanalysis and microscopy by X-ray photoelectron spectroscopy (XPS), core-loss spectroscopy (CLS) and Auger electron spectroscopy (AES) .......... . 89 J. Cazaux Reflection electron microscopy ..................... 127 J.M. Cowley An introduction to reflection high energy electron diffraction ..... 159 P.J. Dobson Intensity oscillations in reflection high energy electron diffraction during epitaxial growth. . ........... 185 P.J. Dobson, B.A. Joyce, J.H. Neave, J. Zhang Emission and low energy reflection electron microscopy ......... 195 E. Bauer and W. Telieps Scanning tunneling microscopy and spectroscopy ............. 235 N. Garcia Spin-polarized secondary electrons from ferromagnets .......... 267 J. Kirschner Electronically stimulated desorption: mechanisms, applications and implications ....................... 285 D. Menzel Structure and catalytic activity of surfaces .............. 301 V. Ponec Subj ect Index . . . . . . . . . . . . . . . . . . . . . . . • • . . . . 315 viii PRINCIPLES AND TECHNIQUES OF TRANSMISSION IMAGING OF SURFACES A. Howie Cavendish Laboratory Madingley Road Cambridge CB3 OHE, U.K. INTRODUCTION Although many surface characterisation techniques are essentially broad beam methods yielding diffraction or other information averaged over large areas of surface, crucial properties of the surface may depend on steps or other inhomogeneities. There is indeed an instability, shown schematically in figure 1, whereby even a uniform single crystal overgrowth such as an expi taxial layer or adsorbed oxide tends to become inhomogeneous, forming island structures or localised defects. The overgrowth has an energy E proportional to thickness t at small t where it matches its lattice parameter with the substrate crystal at the cost of elastic strain energy (point A). At larger values of t, when elastic strain energy becomes prohibitive, misfit dislocations are introduced to relieve it. Eventually where the overgrowth has completely relaxed to its own lattice parameter, E becomes the characteristic interfacial energy of the boundary, independent of t (point C). Since the E versus t curve is concave downwards, a homogeneous film represented by point B can reduce its energy to the point D by breaking up into regions A and C. The study of these important and almost inevitable inhomogeneous features of extended surfaces, as well as of more obviously heterogeneous surface structures like catalyst particles, clearly requires a high resolution, real space imaging technique. For such a purpose, electron E Ifn' 1111 'fIIJ 11110111111111 \ - B I\I ~ ~ ~ ~ ~ ~ C ~ 0 A Fig. 1. Energy per unit area of an epitaxial overgrowth as a function of thickness t, showing instability at B.
The list of books you might like
