Reflection High-Energy Electron Diffraction and Reflection Electron Imaging of Surfaces

525 Pages·1989·15.556 MB·English

by  S. Ino (auth.), P. K. Larsen, P. J. Dobson (eds.)

Reflection High-Energy
Electron Diffraction
and Reflection Electron
Imaging of Surfaces
NATO ASI Series
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Series B: Physics
Reflection High-Energy
Electron Diffraction
and Reflection Electron
Imaging of Surfaces
Edited by
P. K. Larsen
Philips Research Laboratories
Eindhoven, The Netherlands
and
P.J. Dobson
Philips Research Laboratories
Redhill, United Kingdom
Plenum Press
New York and London
Published in cooperation with NATO Scientific Affairs Division
Proceedings of a NATO Advanced Research Workshop
on Reflection High-Energy Electron Diffraction
and Reflection Electron Imaging of Surfaces,
held June 15-19,1987,
in Veld hoven, The Netherlands
Library of Congress Cataloging in Publication Data
NATO Advanced Research Workshop on Reflection High-Energy Electron Diffrac
tion and Reflection Electron Imaging of Surfaces (1987: Veldhoven, Netherlands)
Reflection high-energy electron diffraction and reflection electron imaging of
surfaces I edited by P. K. Larsen and P. J. Dobson.
p. cm.-(NATO ASI series. Series B, Physics; v. 188)
"Proceedings of a NATO Advanced Reserach Workshop on Reflection High
Energy Electron Diffraction and Reflection Electron Imaging of Surfaces, held
June 15-19, 1987, in Veldhoven, The Netherlands"-T.p. verso.
"Published in cooperation with NATO Scientific Affairs Division."
Includes bibliographical references and index.
ISBN-13: 978-1-4684-5582-3 e-ISBN-13: 978-1-4684-5580-9
DOl: 10.1007/978-1-4684-5580-9
1. Surfaces (Physics)-Technique-Congresses. 2. Reflection high energy
electron diffraction-Congresses. 3. Reflection electron microscopy-Con
gresses. I. Larsen, P. K. II. Dobson, P. J. III. North Atlantic Treaty Organization.
Scientific Affairs Division. IV. Title. V. Series.
QC173.4.S94N37 1987 88-28843
530.4'1-dc19 CIP
© 1988 Plenum Press, New York
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SPECIAL PROGRAM ON CONDENSED SYSTEMS
OF LOW DIMENSIONALITY
This book contains the proceedings of a NATO Advanced Research Workshop
held within the program of activities of the NATO Special Program on Con
densed Systems of Low Dimensionality, running from 1983 to 1988 as part of
the activities of the NATO Science Committee.
Other books previously published as a result of the activities of the Special
Program are:
Volume 148 INTERCALATION IN LAYERED MATERIALS
edited by M. S. Dresselhaus
Volume 152 OPTICAL PROPERTIES OF NARROW-GAP LOW-DIMENSIONAL
STRUCTURES
edited by C. M. Sotomayor Torres, J. C. Portal, J. C. Maan, and
R. A. Stradling
Volume 163 THIN FILM GROWTH TECHNIQUES FOR LOW-DIMENSIONAL
STRUCTURES
edited by R. F. C. Farrow, S. S. P. Parkin, P. J. Dobson,
J. H. Neave, and A. S. Arrott
Volume 168 ORGANIC AND INORGANIC LOW-DIMENSIONAL CRYSTALLINE
MATERIALS
edited by Pierre Delhaes and Marc Drillon
Volume 172 CHEMICAL PHYSICS OF INTERCALATION
edited by A. P. Legrand and S. Flandrois
Volume 182 PHYSICS, FABRICATION, AND APPLICATIONS OF
MULTILAYERED STRUCTURES
edited by P. Dhez and C. Weisbuch
Volume 183 PROPERTIES OF IMPURITY STATES IN SUPERLATTICE
SEMICONDUCTORS
edited by C. Y. Fong, Inder P. Batra, and S. Ciraci
PREFACE
This volume contains the papers presented at the NATO Advanced
Research Workshop in "Reflection High Energy Electron Diffraction and
Reflection Electron Imaging of Surfaces" held at the Koningshof conference
center, Veldhoven, the Netherlands, June 15-19, 1987.
The main topics of the workshop, Reflection High Energy Electron
Diffraction (RHEED) and Reflection Electron Microscopy (REM), have a common
basis in the diffraction processes which high energy electrons undergo when
they interact with solid surfaces at grazing angles. However, while REM is
a new technique developed on the basis of recent advances in transmission
electron microscopy, RHEED is an old method in surface crystallography
going back to the discovery of electron diffraction in 1927 by Davisson and
Germer. Until the development of ultra high vacuum techniques in the
1960's made instruments using slow electrons more accessable, RHEED was the
dominating electron diffraction technique. Since then and until recently
the method of Low Energy Electron Diffraction (LEED) largely surpassed
RHEED in popularity in surface studies. The two methods are closely
related of course, each with its own specific advantages. The grazing
angle geometry of RHEED has now become a very useful feature because this
makes it ideally suited for combination with the thin growth technique of
Molecular Beam Epitaxy (MBE). This combination allows in-situ studies of
freshly grown and even growing surfaces, opening up new areas of research
of both fundamental and technological importance. The workshop and this
volume reflect the revitalization of the old method of RHEED as well as the
introduction of new surface sensitive electron microscopy techniques.
The workshop was made possible due to the generous support by Nato
Scientific Affairs Division, Brussels, Belgium. We should like to thank
J. M. Cowley, M. G. Lagally and G. Meyer-Ehmsen for their help and advice
in planning the workshop. We also thank Philips Research Laboratories for
assistance with many aspects of the workshop.
P.K. Larsen P.J. Dobson
Philips Research Laboratories Philips Research Laboratories
Eindhoven, the Netherlands Redhill, UK
INTRODUCTION
The main theme of the workshop. reflection high energy electron dif
fraction (RHEED) covered almost all aspects of electron diffraction from
surfaces at glancing angles. e.g: basic diffraction mechanisms at perfect
surfaces. influences of defects and disorder. the role of inelastic scat
tering etc. The second important theme of the workshop. reflection elec
tron microscopy (REM) uses diffraction principle in common with RHEED and
is capable of producing direct images of atomic steps and defects on
surfaces. Imaging techniques using low energy electrons at near normal
incidence were also included in the workshop. In the following we briefly
introduce the different sections into which the topics of the workshop have
been organized in this volume.
The first chapter deals with experimental and theoretical aspects of
surface structure determination. Whilst the qualitative interpretation of
RHEED patterns has been well established for many years. a quantitative
interpretation of the absolute and even relative intensities is lacking.
In particular. the intensity of the specular beam when recorded as a func
tion of the incident glancing angle (rocking-curve) should provide infor
mation which will enable the surface crystallographic structure to be
uniquely determined. Considerable progress has been made in this area
using dynamical calculations. but as demonstrated in this section. the more
simple kinematic approach still plays an important role. particularly for
the elimination of unsuitable crystallographic models. This section also
discusses some aspects of inelastic scattering in RHEED and reflection
imaging.
Some further consequences of inelastic scattering are dealt with in
the second section which is devoted to resonance and channeling. Surface
or bulk resonance effects can have a very large influence 0 the measured
elastic and inelastic scattering intensities and recognition of the con
ditions is important. These effects can be exploited to enhance Auger
electron or x-ray yields for surface microanalysis.
The third chapter covers aspects of diffraction by real surfaces which
may have many different types of defects and disorder. e.g: mosaic struc
ture. steps. 3-D islands and anti-phase boundaries associated with differ
ent reconstruction domains. RHEED can yield useful information about such
features and this is particularly important during the growth of thin
epitaxial layers. Many chemical reaction and nucleation phenomena are
strongly affected by the presence of surface defects or disorder and the
detection and characterization of these features by RHEED may be very
significant and useful.
The forth short section deals with convergent beam effects in reflec
tion diffraction. This technique is already proving to be of tremendous
utility in transmission electron microcospy. The use of a convergent probe
allows for many incident polar and azimuthal angles to be explored simul
taneously, i.e: it therefore complements the currently used rocking-curve
data collection technique and, in principle, is much more rapid in appli
cation.
All diffraction techniques can lend themselves to microscopic imaging
and this the topic of chapter five. The chapter is subdivided between
conventional instruments which use a relatively broad incident beam, scan
ning microprobe instruments and low energy electron diffraction instru
ments. It is often said that a picture is worth many words and this
comment is amply justified in this section. Diffraction contrast
mechanisms need to be understood in order to interprete all of the details
offered in reflection microscope images - this is where the main link comes
with the other sections of the volume. There is generally good agreement
between the distorted and foreshortened reflection high energy images of
surface steps, reconstruction and defects and the non-distorted low energy
electron reflection microscope images.
The final chapter deals with different aspects of RHEED applied to the
study of the growth of epitaxial films. The section is subdivided for
convenience into experimental studies of the growth of semiconductors and
metals and the theoretical aspects of time dependent RHEED intensity vari
ations. The main topic is the interpretation of the oscillations of inten
sity in RHEED when epitaxy occurs in a layer by layer growth mode. This
topic has technological as well as scientific importance since it allows
for precise measurements and control of the growth rate and conditions in
molecular beam epitaxy and related growth techniques, and the determination
of the kinetics of surface processes.
The full potential of RHEED and reflection electron imaging has not
yet been fully realized. We hope that this book will be a useful point of
reference and stimulation to others in this and related fields.
x
CONTENTS
SURFACE STRUCTURAL DETERMINATION
EXPERIMENTAL
Experimental Overview of Surface Structure Determination
by RHEED
S. Ino 3
THEORY
Surface Structural Determination Using RHEED
J .L. Beeby 29
Theory of RHEED by Reconstructed Surfaces
M.G. Knibb and P.A. Maksym 43
Accurate Dynamical Theory for RHEED Rocking-curve Intensity
Spectra
S.Y. Tong, T.C. Zhao and H.C. Poon 63
INELASTIC EFFECTS
Inelastic Scattering Effects in RHEED and Reflection Imaging
A.L. Bleloch, A. Howie, R.H. Milne and M.G. Walls 77
Excitation of Dielectric Spheres by Electron Beams
P.M. Echenique 91
RESONANCE AND CHANNELING EFFECTS
Resonance Effects in RHEED
G. Meyer-Ehmsen 99
Inelastic Scattering and Secondary Electron Emission Under
Resonance Conditions in RHEED from Pt(lll)
H. Marten 109
Adatom Site Determination Using Channeling Effects in RHEED
on X-ray and Auger Electron Production
J.C.H. Spence and Y. Kim 117
xi
A Note on the Bloch Wave and Integral Formulations of RHEED
Theory
Jon Gj¢nnes 131
DISORDERS AND STEPS IN ELECTRON DIFFRACTION
Diffraction from Disordered Surfaces: An Overview
M.G. Lagally, D.E. Savage and M.C. Tringides 139
Theory of Electron Scattering from Defec~: Steps on Surfaces
with Non-equivalent Terraces
W. Moritz 175
Diffraction from Stepped Surfaces
M. Henzler 193
RHEED and Disordered Surfaces
B. Bolger, P.K. Larsen and G. Meyer Ehmsen 201
Temperature Diffuse Scattering in RHEED
M. Albrecht and G. Meyer-Ehmsen 211
Temperature+Dependence of the Surface Disorder on Ge(OOl) Due
to Ar Ion Bombardment
A.J. Hoeven, J.S.C. Kools, J. Aarts and P.C. Zalm 217
Two-dimensional First-order Phase Separation in an Epitaxial
Layer
T.-M. Lu and S.-N. Yang 225
CONVERGENT BEAM DIFFRACTION
Surface Convergent-Beam Diffraction for Characterization and
Symmetry Determination
J.A. Eades and M.D. Shannon 237
Convergent Beam RHEED Calculations Using the Surface Parallel
Multislice Approach
A.E. Smith 251
REFLECTION ELECTRON MICROSCOPY
USING CONVENTIONAL INSTRUMENTS
Reflection Electron Microscopy in TEM and STEM Instruments
J.M. Cowley 261
Reflection Electron Microscopy with Use of CTEM: Studies of Au
Growth on Pt(lll)
K. Yagi, S. Ogawa and Y. Tanishiro 285
Application of Reflection Electron Microscopy for Surface Science
(observation of cleaned crystal surfaces of Si, Pt, Au and Ag)
Y. Uchida 303
Reflection Microscopy in a Scanning Transmission Electron
Microscope
R.H. Milne 317