Physics of Nonmetallic Thin Films

507 Pages·1976·22.53 MB·English

by  A. Cachard (eds.)

Physics of
Nonmetallic Thin Films
N ATO ADVANCED STUDY INSTITUTES SERIES
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Physics of
Nonmetallic Thin Films
Edited by
C. H. S. Dupuy and A. Cachard
Universite Claude Bernard Lyon 1
Villeurbanne,Jlrance
PLENUM PRESS. NEW YORK AND LONDON
Published in cooperation with NATO Scientific Affairs Division
Library of Congress Cataloging in Publication Data
Nato Summer School on Metallic and Nonmetallic Thin Films, 2d, Corsica, 1974.
Physics of nonmetallic thin films.
(NATO advanced study institutes series: Series B. Physics; v. 14)
Includes index.
1. Nonmetallic materials- Addresses, essays. lectures. 2. Thin fIlms- Addresses, es-
says. lectures. I. Dupuy. Claude H. S. II. Cachard, A. III. Title. IV. Series.
QC176.N38 1974 530.4'1 76-8385
ISBN-13: 978-1-4684-0849-2 e-ISBN-13: 978-1-4684-0847-8
DOl: 10.1007/978-1-4684-0847-8
Lectures presented at the Second NATO Summer School on
Metallic and Nonmetallic Thin Films held in Corsica. Serra di Ferro.
September 1-5. 1974
© 1976 Plenum Press, New York
Softcover reprint of the hardcover 1st edition 1976
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Preface
For several years now the intense development in the field of
microelectronics, the interest in coating materials, and activity
in integrated optics have produced many advances in the field of
thin solid filmg~
The research activity has become so intensive and so broad
that it is necessary to divide the field into metallic and non
metallic thin films. A summer school in the area of non metallic
thin films appeared to be a very fruitful concept and, hence, in
October, 1973, A.S.l.M.S. made a proposal to N.A.T.O to hold this
second summer school in Corsica in September 1974.
The basic idea behind this summer school was essentially to
stress and synthesize physical properties and structure of non
metallic thin films. The main reason for this was the feeling that
many laboratories are very specialized and that few engage in both
physical and structural analysis of these films.
The program included a large section on' physical studies:
electrical (transport, interface effects, switching), mechanical
and optical. There was also a large section o~characterization,
crystal structure, chemical composition (stoichiometry is always a
difficult problem), bonding and electronic structure.
Certainly it is different for every laboratory to pursue all
these avenues of research. However, perhaps a good result of this
summer school will be a deeper realization among scientists of the
connection between physical properties and structure. Collaboration
is probably necessary in many of these areas and in this respect I
am sure that the summer school was profitable.
I want to acknowledge the many people who helped me organize
this summer school. I want to especially acknowledge the members of
the scientific committee and the lecturers. I wish to give special
mention to the scientific codirectors, Dr. A. Cachard, Universite
Claude Bernard (Lyon), and Dr. S. Fonash, Penn State University,
and Ms. pivot and Chassagne, treasurer and secretary, respectively.
v
PREFACt
My special thanks to the staff of the Village de Detente et
de Loisirs in Serra di Ferro.
I want to mention especially Mr. A. Paolini, Director and
Mrs Pelamourgue, Assistant.
To all the people of Corsica I give my thanks. I am sure that
no one will forget the friendly reception of Serra di Ferro and its
mayor Mr. J.R. Tomi.
As was the case for the first A.S.I.M.S. summer school in
Porto Vecchio, Mr. J. de Rocca Serra, Chef de la Mission Regionale,
helped us and I thank him.
During this summer school Dr. J. A. Roger presented and defend-
ed his Ph. D. Thesis. It is very pleasant for me to thank him for
presenting this first Ph. D. in Corsica.
The help from N.A.T.O allowed the school to be organized and
permitted it to take place. The D.G.R.S.T. helped us too, and I
thank them.
C.H.S. DUPUY
Contents
General Introduction 1
A.K. Jonscher
Part I
BASIC NOTIONS
Preparation Methods for Thin Films 9
D.S. Campbell
Growth Processes 49
R. Niedermayer
Electronic States in Semiconductors 93
D.A. Greenwood
Part II
CHARACTERIZATION
Structure Determination of Thin Films • . 123
H. Raether
Physico-Chemical Analysis of Thin Films . • . • . . • .. 141
A. Cachard
Thickness Measurements 163
D.S. Campbell
Part III
PHYSICAL PROPERTIES
Electronic Transport Properties • . . . • 189
R.M. Hill
vii
viii CONTENTS
Ionic Transport in Thin Films . • • • • • . . • . • • •• 219
S.J. Fonash
Dielectric Properties of Thin Films: Polarization
and Effective Polarization . . • . . . . • . 225
S.J. Fonash
Threshold Switching: A Discussion of Thermal and
Electronic Issues • • • . . • . . 253
H.K. Henisch and C. Popescu
Mechanical Properties of Non-Metallic Thin Films 273
R. W. Hoffman
Thin Films in Optics 355
G. Baldini and L. Rigaldi
Radiation Effects in Thin Films 383
A. Holmes-Siedle
Part IV
APPLICATIONS
Thin Film Applications in Microelectronics 417
V. Le Goascoz
Application of Thin Non-Metallic Films in Optics 445
E. Pelletier
Some Applications of Non-Metallic Thin Films 459
M.H. Francombe
List of Participants 495
Index 501
GENERAL INTRODUCTION
A.K. Jonscher
Chelsea College, University of London
Pulton Place, London SW6 5PR. U.K.
The purpose of this Introduction is to attempt to place the
subject of Non-Metallic Thin Films into proper perspective against
the more general background of modern physics and technology and
also to discuss some problems relevant to research policiy in this
field.
The fist question that may be asked is : "What is so signifi-
cant in this subject that it should have been chosen as the theme
of a specialist Summer School? ". The answer to this, in my opi-
nion, is that thin non-metallic films are commonly found in natu-
re, that they have many useful applications and that their physi-
cal properties present certain unique feature which are not normal-
ly associated with bulk materials.
From the standpoint of a Summer School, with its definite di-
dactic purpose, the subject of Thin Films is uniquely suited as a
vehicle for conveying to the student a wide range of specialist
topics - it is a multidisciplinary field which is both challenging
and rewarding asa subject of study, provided care is taken to ap-
proach it in the correct manner- I shall have something more to say
about this later.
It is desirable at the outset to define what is meant by the
term "Thin Films". The commonly accepted limitation at the upper
end of thickness is the concept of Ii Thick Films", typically some
tens of micrometers in thickness. Thus it would appear that we would
be justified to describe films up to one micrometer in thickness
as "thin", without placing too much significance on the precise fi-
gure. However, even 1 ~m contains some four thousand atomic layers
and it may have many properties of "bulk" material. Figure 1 shows
schematically some relevant orders of magnitude.
2 A.K. JONSCHER
Thin Thick
Mono- ShAric
Ia.yer Acid
1A II I 1mm
0.1 1 10 nm
5 I. ..... .1
cree rlln g lunnel'''f
distanc.e
in meta.1s
Fig. 1 Typical order of magnitude relating to thin non-metallic
films.
Whether the behaviour of a thin film is distinct from that of
the corresponding bulk material depends upon the precise context.
Thus the structure may be influenced by interfacial processes, e.g.
epitaxy or strain due to lattice mismatch and this may carryon
for hundreds of atomic layers from the interface. The elec-trical
properties will be determined by the relation between the mean free
path and the film thickness - in very disordered non-metallic films
the mean free path is effectively the tunnelling distance, of the
order of 5 nm and thus most films are bulk-like from this point of
view. However, this is not so in metallic or highly crystalline
films in which the mean free path may be significantly large than,.
say, 10 nm and thus film thickness may become a limitation. The
electrical effect of the interface may extend to several Debye
lengths into the material and this, as we shall see in Dr. Fonash's
lectures, may be a serious consideration. in non-metallic films, but
it is not important in metallic ones where the screening length is
of the order of 0.1 nm, or less than one atomic layer.
Not much will be said in the context of the present Summer
School of very thin films - of tunnelling thickness - nor of the
problem of quantisat.ion of energy levels in the direction normal
to the plane of the film. Some of these questions are however im-
plicit, for example, in the operation of MNOS transistors, as dis-
cussed by Dr. Le Goascoz.
The presence on metallic surfaces of naturally occuring oxide
and other films was known for a long time to influence their opti-
cal and electrical properties. Where the films are mechanically ro-
bust and chemically inert, as in the case of aluminium, tantalum
and silicon, they may act as protective coatings and they have been