A.V. Chadwick M. Terenzi Editors Defects in Solids Modern Techniques Defects in Solids Modern Techniques 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 D. Reidel Publishing Company and Physical Sciences Dordrecht, Boston, and Lancaster D Behavioral and Social Sciences Martinus Nijhoff Publishers E Engineering and The Hague, Boston, Dordrecht, and Lancaster Materials 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 139-New Vistas in Nuclear Dynamics edited by P. J. Brussaard and J. H. Koch Volume 140-Lattice Gauge Theory: A Challenge in Large-Scale Computing edited by B. Bunk, K. H. MOtter, and K. Schilling Volume 141-Fundamental Problems of Gauge Field Theory edited by G. Velo and A. S. Wightman Volume 142-New Vistas in Electro-Nuclear Physics edited by E. L. Tomusiak, H. S. Caplan, and E. T. Dressier Volume 143-Atoms in Unusual Situations edited by Jean Pierre Briand Volume 144-Fundamental Aspects of Quantum Theory edited by Vittorio Gorini and Alberto Frigerio Volume 145-Atomlc Processes in Electron-ion and lon-lon Collisions edited by F. Brouillard Volume 146-Geophysics of Sea Ice edited by Norbert Untersteiner Volume 147-Defects in Solids: Modern Techniques edited by A. V. Chadwick and M. Terenzi Series B: Physics Defects in Solids Modern Techniques Edited by A. V. Chadwick University of Kent Canterbury, England and M. Terenzi University of Calabria Renole, Italy Springer Science+Business Media, LLC Proceedings of a NATO Advanced Study Institute, held September 16-27, 1985, in Cetraro, Calabria, Italy Library of Congress Cataloging in Publication Data NATO Advanced Study Institute (1985: Calabria, Italy) Defects in solids. (NATO ASI series. Series B, Physics; v. 147) Proceedings of a NATO Advanced Study Institute, held September 16-27, 1985, in Cetraro, Calabria, Italy"-T.p. verso. "Published in cooperation with NATO Scientific Affairs Division." Includes bibliographies and index. 1. Solids-Congresses. 2. Crystals-Defects-Congresses. I. Chadwick, A. V. (Alan V.) II. Terenzi, M. (Mario) Ill. North Atlantic Treaty Organizatior• . Scientific Affairs Division. IV. Series. QC176.A1N3 1985 530.4'1 86-25417 ISBN 978-1-4757-0763-2 ISBN 978-1-4757-0761-8 (eBook) DOI 10.1007/978-1-4757-0761-8 © 1986 Springer Science+Business Media New York Originally published by Plenum Press. New York in 1986 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 PREE"ACE Defects in solids are of fundamental interest to scientists in many disciplines and are important to the development of numerous industrial technologies. Knowledge of the nature and behaviour of defects is vital for the detailed understanding of solid state phenomena in chemistry, physics, metallurgy, geology and in the production of catalysts, ceramics, semiconductor components and solid electrolytes. The relevance of defects to many areas of science has long been recognized and a great variety of techniques has evolved for their investigation. However, the last decade has witnessed the introduction of new techniques, both experimental and theoretical, which together with major developments in existing methods have greatly increased the understanding of the defective solid state. These advances, which were often developed for specialized problems, are rapidly growing in their usage and are being applied to a greater diversity of materials. As a consequence, defect research is making considerable progress in both the understanding of long-standing problems and in the complexity of problems that can be investigated. This volume is based on the lectures presented at the NATO Advanced Study Institute held at Cetraro, Italy in 1985. The aim is to survey the recent developments in the techniques used in defect investigations. These can broadly be divided into three classes. Firstly, there are the laboratory-based experiments where developments in electronics, lasers and spectrometers have led to new or i:nproved methods which allow the research scientist to undertake sophisticated studies in a university or company laboratory. Typical examples are the positron annihilation technique (PAT), various forms of magnetic resonance spectroscopy and complex impedance spectroscopy. The second class of techniques rely on the special experimental probes provided by large, centralized facilities such as neutron and synchrotron radiation sources. Examples here include the range of neutron scattering techniques, extended X-ray absorption fine structure (EXAFS), X-ray topography and a variety of surface experiments. The number of these facilities has increased (and is still growing) and many scientists now have access to the instruments. Thus the horizons for the scientist interested in defects has been widened. Finally, there have been rapid developments in the applications of computer simulation to defect studies. These have been possible partly due to the improvements in computers (in speed and memory capabilities) and to the methods that have been evolved to represent interatomic potentials. In order to present a structured coverage of the topics the chapters have been arranged so that the contents follow the general sequence: v (i) introductory background to defects; (ii) techniques used to investigate the structure of defects; (iii) computer simulation techniques; (iv) techniques used to investigate defects on surfaces; (v) techniques used to investigate the transport of atoms via defects. The boundaries between these five sections should not be taken as rigorous and there is naturally some overlap which is in fact desirable. In Chapter 1 Corish surveys the variety of types of defects that are found in solids and lays the foundation for the rest of the volume. This is followed by two short introductory chapters. In Chapter 2 Chadwick outlines some of the objectives of point defect investigations in ionic solid. Cormack considers the objectives of theoretical studies and the links to experiments in Chapter 3. The ability of transmission electron microscopy to directly observe the structure of individual defects makes it an extremely powerful technique and it is described by Hobbs in Chapter 4. Stewart in Chapter 5 reviews neutron scattering by defects in solids and shows how the various experiments can be used to probe a wide range of defect types. In Chapter 6 Beech concentrates on the specific uses of neutrons to probe static defects in complex materials and in studies of superionic solids. The theme of defect structures is maintained in Chapter 7 where Eldrup covers the applications of the positron annihilation technique. Sauvage-Simkin describes the use of synchrotron radiation in the study of defects in Chapter 8. This includes X-ray topography and related methods and points out the novel applications in the study of surfaces. In Chapter 9 Spaeth reviews the exciting developments in the spectroscopic studies of defects. This includes the applications to complex, but important materials used in microelectronics. Nuclear magnetic resonance spectroscopy has been extensively used to study point defects in ionic crystals and the basic principles are outlined by Strange in Chapter 10. The specific applications of this technique in diffusion studies are treated in Chapter 11 by Terenzi. Ten years ago the computer simulation of defects was in its infancy, but it has matured very rapidly. In Chapter 12 Catlow reviews the range of simulation methods that can now be regarded as well-established. This is followed by a short contribution by Harding in Chapter 13 which covers the recent developments in the calculation of defect entropies. Chapter 14 by Henrich moves to the area of surface defects and their investigation by electron spectroscopy. In contrast to bulk defects relatively little is known about surface defects. However, this chapter shows where progress is being made and the promise offered by new techniques for an increased understanding of this complex topic. One of the new techniques is computer simulation of surface defects and this is specifically reviewed in Chapter 15 by Col bourn. The remaining chapters are concerned with the migration of defects. Philibert in Chapter 16 reviews atomic diffusion in metals. This is probably the most thoroughly investigated area of defect physics and has helped to develop many of the general ideas concerning atomic transport in materials. An area that has been growing over recent years is the study of diffusion in oxides and this is surveyed by Monty in Chapter 17. A short contribution by Chadwick and Corish in Chapter 18 considers the specific case of ionic conductance measurements in solids, both single crystals and ceramic pellets. The final chapter by Capelletti reviews the thermally stimulated depolarization technique. This essentially simple but very powerful technique for studying impurity-defect clusters in ionic solids is now being used to investigate a wide range of materials. The appendix contains short contributions which were presented at the Advanced Study Institute. They have been included to exemplify the types and range of defect studies that are presently in progress. It has not been possible to include a detailed treatment of every technique and there are some important omissions of which we are fully aware. Nevertheless, this book should give the reader a clear view of the defect techniques that are currently available and serve as a very useful reference source. A feature that we hope will prove attractive to the reader is that in addition to outlining the basic principles of techniques the contributors have described the applications and the scope for extending them to various types of material and problems. We thank the authors for taking this very helpful approach. Finally, we hope that the book conveys the enthusiasm that is being created by the new techniques. A.V. Chadwick M. Terenzi ACKNOWLEDGEMENTS We would like to thank NATO for their support of the Advanced Study Institute which formed the basis of this book. In addition, we would like to thank the following organisations for their support: the British Council, British Petroleum plc, Cassa di Risparmadi Calabria e Lucania, Consiglio Nazionale delle Ricerche, ENEA, United States Army European Research Office, University of Calabria and the University of Kent. We are indebted to the organising committee and the lecturers at the ASI. They put in a considerable effort in making the meeting successful and also worked extremely hard on the chapters presented in this book. Finally we would like to thank Mrs. Heather Harrow for general secretarial assistance and we are especially grateful to Mrs. Eileen Stoydin for her efficient work in the preparation of the manuscripts. Alan Chadwick Mario Terenzi ix CONTENTS Introduction to Defects in Solids ..•.•..•..•••.•..••.•.••.••••..... J. Corish Experimental Studies of Point Defects: The example of Crystals with the Fluorite Structure............................ 37 A.V. Chadwick Objective of Theoretical Studies and their Links with Experiment. • • • . • • . . . . • . . • • . . . . • . • . • • • . • • • . • • • • • • . . • • . . . . • • • 51 A.N. Cormack Transmission Electron Microscopy of Defects in Solids.............. 61 L.W. Hobbs Neutron Scattering from Defects in Materials....................... 95 R.J. Stewart Elastic Neutron Diffraction and Defect Structures.................. 131 F.W. Beech Application of the Positron Annihilation Technique in Studies of Defects in Solids................................. 145 M. Eldrup X-Ray Topography and related Techniques using Synchrotron Radiation..................................... 179 M. Sauvage-Simkin Spectroscopic Studies of Defects in Ionic and Semi-Ionic Solids................................................ 205 J-M. Spaeth Principles of NMR: Its uses in Defect Studies...................... 243 J.H. Strange Transport Studies using NMR........... . • • • . . • . . • . • • • . • . . . . . • . . . • • . . 255 M. Terenzi Computer Simulation of Defects in Solids . . . • • . . • . • . . . • • . • . • . . . • . . . • 269 C.R.A. Catlow Calculation of Defect Processes at High Temperature................ 303 J.H. Harding The Nature of Defects on Solid Surfaces as Studied by Electron Spectrscopy........................................ 311 V.E. Henrich xi