Ionization of Solids by Heavy Particles NATO AS! 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 and Physical Sciences Kluwer Academic Publishers D Behavioral and Social Sciences Dordrecht, Boston, and London E Applied Sciences F Computer and Systems Sciences Springer-Verlag G Ecological Sciences Berlin, Heidelberg, New York, London, H Cell Biology Paris, Tokyo, Hong Kong, and Barcelona I Global Environmental Change Recent Volumes in this Series Volume 303—Particle Production in Highly Excited Matter edited by Hans H. Gutbrod and Johann Rafelski Volume 304—Growth Patterns in Physical Sciences and Biology edited by Juan-Manuel Garcia-Ruiz, Enrique Louis, Paul Meakin, and Leonard M. Sander Volume 305—Chemical Physics of Intercalation II edited by Patrick Bemier, John E. Fischer, Siegmar Roth, and Stuart A. Solin Volume 306—Ionization of Solids by Heavy Particles edited by Raul A. Baragiola Volume 307—Negative Differential Resistance and Instabilities in 2-D Semiconductors edited by N. Balkan, B. K. Ridley, and A. J. Vickers Volume 308 —Photonic Band Gaps and Localization edited by C. M. Soukoulis Volume 309 —Magnetism and Structure in Systems of Reduced Dimension edited by Robin F. C. Farrow, Bernard Dieny, Markus Donath, Albert Fert, and B. D. Hermsmeier Series B: Physics Ionization of Solids by Heavy Particles Edited by Raul A. Baragiola University of Virginia Charlottesville, Virginia Springer Science+Business Media, LLC Proceedings of a NATO Advanced Research Workshop on Ionization of Solids by Heavy Particles, held June 1-5,1992 , in Taormina, Ital y NATO-PCO-DATA BASE The electroni c inde x t o th e NATO ASI Serie s provides ful l bibliographica l reference s (wit h keywords and/o r abstracts ) t o mor e tha n 30,00 0 contribution s fro m internationa l scientist s published i n al l sections o f th e NATO ASI Series. Access t o th e NATO-PCO-DATA BASE is possible in two ways: —vi a online FILE 12 8 (NATO-PCO-DATA BASE) hosted by ESRIN, Via Galileo Galilei, I-00044 Frascati, Italy —vi a CD-ROM "NATO-PCO-DATA BASE" wit h user-friendly retrieva l softwar e i n English, French, and German (©WTV GmbH and DATAWARE Technologies, Inc . 1989 ) The CD-ROM ca n b e ordered throug h an y membe r of th e Boar d o f Publishers o r throug h NATO-PCO, Overijse, Belgium. Library of Congress Cataloging-in-Publication Data Ionization of solids by heavy particles / edited by Raul A. Baragiola. p. cm. — (NATO ASI series. Series B, Physics ; v. 306) "Published in cooperation with NATO Scientific Affairs Division." "Proceedings of a NATO Advanced Research Workshop on Ionization of Solids by Heavy Particles, held June 1-5, 1992, in Taormina, Italy." Includes bibliographical references and index. ISBN 0-306-44489-5 1. Condensed matter—Effect of radiation on—Congresses. 2. Ionization—Congresses. 3. Heavy particles (Nuclear physics)- -Congresses. 4. Electrons—Emission—Congresses. 5. Auger effect¬ -Congresses. I. Baragiola, Raul A. II. North Atlantic Treaty Organization. Scientific Affairs Division. III. NATO Advanced Research Workshop on Ionization of Solids by Heavy Particles (1992 Taormina, Italy) IV. Series. QC173.4.C65I67 1993 530.4'16—dc20 93-8373 CIP ISBN 978-1-4613-6229-6 ISB N 978-1-4615-2840-1 (eBook ) DOI 10.1007/978-1-4615-2840-1 © Springer Science+Business Media New York 1993 Originally published by Plenum Press, New York 1993 All rights reserved No part of this book may be reproduced, stored i n retrieval system, or transmitte d i n any form or by any means, electronic, mechanical, photocopying, microfilming , recording, or otherwise, without written permission from the Publisher PREFACE This book collects the papers presented at the NATO Advanced Research Workshop on "Ionization of Solids by Heavy Particles", held in Giardini-Naxos (Taormina), Italy, on June 1 - 5, 1992. The meeting was the first to gather scientists to discuss the physics of electron emission and other ionization effects occurring during the interaction of heavy particles with condensed matter. The central problem in the field is how to use observations of electron emission and final radiation damage to understand what happens inside the solid, like excitation mechanisms, the propagation of the electronic excitation along different pathways, and surface effects. The ARW began with a brief survey of the field, stressing the unknowns. It was pointed out that ionization theories can only address the very particular case of weak perturbations. For this problem, this meant high speed, low-charged projectiles (a perturbation treatment of interactions with slow, highly charged ions was later presented). Only semi-empirical models exist for velocities lower than the Fermi velocity in the solid, which can be used to predict kinetic electron emission yields. These models, however, do not address the basic questions about the mechanisms for electron excitation, transport and escape through the surface layer. Theories of electron emission have not reached yet the point where they can be used to justify more predictive, semi-empirical models. The popular Monte Carlo descriptions of electron motion in solids still need to address conflicts with Heisenberg's principle. Structures in electron energy distribution, attributed to the decay of bulk and surface plasmons, do not follow theoretical expectations. Free-electron gas theories, which have been used successfully to predict electronic stopping do not pass the closer test of predicting individual electronic excitations. Data on extrapolated thresholds in the electron yields contradict these models and remain unexplained. New developments presented at the meeting, using atomic approaches may be able to solve this problem and show that electron excitation requires the presence of the atomic cores. Other questions identified as part of the conclusions include: decay pathways of "hollow" atoms in solids, the description of electronic states at the surface in the presence of an outside charge, the description of elastic scattering surfaces of ionic crystals, the identification of excitation mechanisms at eV energies, the role of electron loss from the projectile in total electron yields, the origin of Z3 deviations from the Born approximation, the atomic description in inelastic events at low velocities, the description of valence wave functions in solids far from equilibrium, the origin of non-Poisson statistics in electron emission, the origin of unusually high probability of no electron emission for slow ions traversing thin foils, the probability of multiple electron excitation in Auger neutralization at surfaces, the potential of ion tracks in solids and its time evolution, the role of structural effects in electron emission, and the explanation of anomalous ionization effects, electric fields and breakdown inside irradiated insulators. v This workshop was possible thanks to financial support from the NATO Scientific Affairs Division, the Italian Consiglio Nazionale delle Richerche, the University of Calabria and the University of Catania. I express my special gratitude to Tonino Oliva and Giovanni MarIetta for obtaining financial support from Italian sources, for the smooth operation of the workshop and for showing that savoir vivre can coexist with successful scientific meetings. I would like to thank the other members of the International committee: Fernando Flores, Wolfgang O. Hofer and Tonino Oliva for their help and advice during the organization of the ARW. I am grateful to Pam Lockley and David Grosjean, who were very helpful during the preparation of this book. Finally, I am particularly thankful to the participants, the truly essential actors, who made this meeting a success through their cooperation, enthusiasm, and, above all, their piercing critique and critical inquiries. Raul A. Baragiola Director of the NATO ARWon Ionization of Solids by Heavy Particles vi CONTENTS THEORY OF IONIZATION AND ELECTRON EMISSION Theory of Electron Ejection from Matter by Highly Charged Ion Impact 1. H. Macek ....................................................................................................................... Dynamic Interaction oflons with Condensed Matter Using a LCAO Approach F. Flores, 1. J. Dorado, F. 1. Garcia-Vidal, 1. Ortega and R. Monreal................................ 11 Promotion of Electronic Levels in Bombarded Solids z. Sroubek and G. Falcone .............................................................................................. 19 Theory oflon-induced Kinetic Electron Emission from Solids M. Rosier....................................... .................. ... ..... ......... ... .... ......................... .... .......... 27 Particle-induced Electron Emission: Open Questions, Pitfalls, and a Few Attempts at Answers P. Sigmund...................................................................................................................... 59 AUGER PROCESSES AT METALLIC SURFACES Auger Processes at Surfaces A. Niehaus.................................................................................................................... 79 Electrons from