Table Of ContentThin Film Device
Agglications
Thin Film Device
A{lfllications
KASTURI LAL CHOPRA
AND
INDERJEET KAUR
Indian Institute of Technology
New Delhi, India
PLENUM PRESS • NEW YORK AND LONDON
Library of Congress Cataloging in Publication Data
Chopra, Kasturi, L., 1933-
Thin film device applications.
Bibliography: p.
Includes index.
1. Thin film devices. I. Inderjeet Kaur. II. Title.
TK7872.T55C48 1983 621.381'71 83-9632
ISBN-13: 978-1-4613-3684-6 e-ISBN-13: 978-1-4613-3682-2
001 10.1007/978-1-4613-3682-2
© 1983 Plenum Press, New York
Softcover reprint of the hardcover 151 ed ilion 1983
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
Dedicated
to the Cause of
Science and Technology
in the Service of
Mankind
Preface
Two-dimensional materials created ab initio by the process of condensation
of atoms, molecules, or ions, called thin films, have unique properties
significantly different from the corresponding bulk materials as a result of
their physical dimensions, geometry, nonequilibrium microstructure, and
metallurgy. Further, these characteristic features of thin films can be drasti
cally modified and tailored to obtain the desired and required physical
characteristics. These features form the basis of development of a host of
extraordinary active and passive thin film device applications in the last
two decades. On the one extreme, these applications are in the submicron
dimensions in such areas as very large scale integration (VLSI), Josephson
junction quantum interference devices, magnetic bubbles, and integrated
optics. On the other extreme, large-area thin films are being used as selective
coatings for solar thermal conversion, solar cells for photovoltaic conver
sion, and protection and passivating layers. Indeed, one would be hard
pressed to find many sophisticated modern optical and electronic devices
which do not use thin films in one way or the other.
With the impetus provided by industrial applications, the science and
technology of thin films have undergone revolutionary development and
even today continue to be recognized globally as frontier areas of RID
work. Major technical developments in any field of science and technology
are invariably accompanied by an explosion of published literature in the
form of scientific publications, reviews, and books. So vast is this rapidly
expanding field that it is not humanly possible to write a comprehensive
treatise on the subject in a single volume, and thus only specialized mono
graphs and edited reviews appear in the literature. Thin Film Phenomena,
by K. L. Chopra (1969), and Handbook of Thin Film Technology, edited
by L. Maissel and G. GIang (1970), provide good early reviews of the
science and technology of thin films, along with a limited description of
thin film device applications. Specialized applications of thin films are
covered in such books as Science and Technology of Surface Coatings,
edited by B. N. Chapman and J. C. Anderson (1973); Thin Film Optical
Filters, by H. A. Macleod (1969); Active and Passive Thin Film Devices,
vii
viii Preface
edited by J. C. Coutts (1978); Polycrystalline and Amorphous Thin Films
and Devices, edited by L. Kazmerski (1980); and Thin Film Solar Cells,
by K. L. Chopra and S. R. Das (1983). The need for a single, concise,
cohesive, and comprehensive textbook on thin film device applications
clearly exists and has been felt by graduate students and workers in the
field. We were inspired by Prof. D. S. Campbell to fill this gap, and the
result is this monograph. Though overly concise, this book provides a
self -contained coverage of a wide range of device applications of thin films
in such areas as optics, electro-optics, microelectronics, magnetics, quantum
engineering, surface engineering, and thermal detection.
What thin films are and how these are prepared and characterized
forms the Introduction (Chapter 1). The role of thin films in a wide range
of optical and electro-optical applications is described in Chapters 2 and
3. This is followed by the micro-electronic and magnetic applications in
Chapters 4 and 5. The super conducting properties and quantum tunneling
effects of thin films are the basis of a host of quantum engineering applica
tions which are the subject of Chapter 6. Thermal applications of thin films
are discussed in Chapter 7. Finally, a whole range of passivating, tribologi
cal, decoration, and biomedical applications form the subject matter of
Chapter 8.
The emphasis in all chapters is to give a brief physical basis and
technical description of the devices in a cohesive manner. Adequate referen
ces are provided for the interested reader to dig deeper into the details of
the devices. Both academically interesting and commercially viable devices
have been covered to inspire the innovative mind. Besides serving as a
textbook for graduate students in applied sciences and engineering, it should
be a good reference book for scientists and engineers involved in RID
work on thin-film-based devices.
A book of this type draws heavily and unhesitatingly from the published
works of numerous authors. We have made a concerted effort to describe
representative examples of applications of thin films from the literature in
various areas in a very condensed and brief form. If we have made some
glaring errors or omissions, we would be grateful to the reader for pointing
these out to us. It is our earnest hope that this unique book will find wide
acceptance as a textbook which will inspire our readers to explore the vast
and virgin field of the micro science and technology of low-dimensional
thin film materials.
We acknowledge the assistance of our colleagues in the Thin Film
Laboratory of our Institute in various forms in the preparation of this book.
We are indebted to Mr. Irfan Habib for his critical reading of the entire
manuscript.
Finally, we are indebted to our families whose exemplary patience
and moral support have sustained us to the completion of this work.
New Delhi K. L. Chopra and I. Kaur
Contents
Chapter 1. Thin Film Technology. An Introduction 1
1.1. Why Thin Films? . . . . . . . . . . . . . . . . . 1
1.2. Thin Film Growth Process . . . . . . . . . . . . . 2
1.2.1. Structural Consequences of the Growth Process 6
1.2.2. Solubility Relaxation .... . 12
1.3. Vapor Deposition Techniques .... . 13
1.3.1. Physical Vapor Deposition (PVD) 13
1.3.2. Chemical Vapor Deposition (CVD) 25
1.4. Solution Deposition Techniques 30
1.4.1. Chemical Solution Deposition (CSD) 31
1.4.2. Electrochemical Deposition (ECD) 37
1.5. Thick Film Deposition Techniques 40
1.5.1. Liquid-Phase Epitaxy (LPE) 40
1.5.2. Screen Printing . . . . . . 41
1.5.3. Melt Spinning ..... . 42
1.5.4. Dip Coating, Spinning, and Solution Casting 42
1.6. Monitoring and Analytical Techniques ..... 43
1.6.1. General Remarks . . . . . . . . . . . . 43
1.6.2. Deposition Rate and Thickness Measurement 43
1.6.3. Structural Analysis 47
1.6.4. Composition Analysis 50
1. 7. Microfabrication Techniques 51
Chapter 2. Thin Films In Optics 55
2.1. Optics of Thin Films ...... . 55
2.2. Antireflection Coatings (AR Coatings) 58
2.2.1. Single-Layer AR Coatings . . 59
2.2.2. Double-Layer AR Coatings 60
2.2.3. Multilayer and Inhomogeneous AR Coatings 64
2.3. Reflection Coatings . . . . . 66
2.3.1. Metal Reflectors 66
2.3.2. All-Dielectric Reflectors 67
2.4. Interference Filters 68
2.4.1. Edge Filters 69
2.4.2. Band-Pass Filters 71
2.5. Thin Film Polarizers 75
ix
x Contents
2.6. Beam Splitters . . . . . . . 76
2.6.1. Polarizing Beam Splitter 76
2.6.2. Dichroic Beam Splitter 76
2.7. Integrated Optics . . . . . . 77
2.7.1. Waveguides ..... 77
2.7.2. Thin Film Optical Components 79
2.7.3. Passive Devices: Couplers 81
2.7.4. Active Devices . . . . . . . 82
Chapter 3. Optoelectronic Applications 89
3.1. Introduction . . . . . . . . . 89
3.2. Photon Detectors . . . . . . . 90
3.2.1. Photoconductive Detectors 90
3.2.2. Photoemissive Detectors 92
3.3. Photovoltaic Devices ..... 98
3.3.1. Solar Cells: General Analysis 99
3.3.2. Thin Film Solar Cells 108
3.4. Applications in Imaging . . . . . 111
3.5. Electrophotography (Xerography and Electrofax) 114
3.6. Thin Film Displays . . . . . . . . . 115
3.6.1. Electroluminescent (EL) Displays 116
3.6.2. Electrochromic Displays 119
3.7. Information Storage Devices . 121
3.7.1. Introduction ..... 121
3.7.2. Optical Hole Memories 122
3.7.3. Holographic Memories 122
3.8. Amorphous Silicon-Based Devices 127
Chapter 4. Microelectronic Applications 129
4.1. Introduction 129
4.2. Thin Film Passive Components . . . . . 129
4.2.1. Electrical Behavior of Metal Films 130
4.2.2. Dielectric Behavior of Insulator Films 132
4.2.3. Resistors 132
4.2.4. Capacitors . . . . . . . . . . . . 134
4.2.5. Inductors ........... . 142
4.2.6. Conductors (Interconnections and Contacts) 142
4.3. Thin Film Active Components 144
4.3.1. Thin Film Transistor (TFf) 144
4.3.2. Thin Film Diodes . . . . 148
4.4. Thin Film Integrated Circuits 150
4.5. Microwave Integrated Circuits (MICs) 154
4.6. Surface Acoustic Wave (SAW) Devices 156
4.6.1. Introduction 156
4.6.2. SAW Transducer . . 158
4.6.3. SAW Delay Line . . 159
4.6.4. SAW Band-Pass Filter 160
4.6.5. SAW Pulse-Compression Filter 161
Contents xi
4.6.6. SAW Amplifier ..... 162
4.6.7. SAW Guiding Components 163
4.6.8. Other Applications . . . 164
4.7. Charge-Coupled Devices (CCDs) 165
4.7.1. Introduction 165
4.7.2. Principle 165
4.7.3. Applications . . 167
4.8. Thin Film Strain Gauges 168
4.9. Gas Sensors ..... 170
Chapter 5. Magnetic Thin Film Devices 171
5.1. Magnetic Thin Films .... . 171
5.1.1. Introduction .... . 171
5.1.2. Uniaxial Anisotropy (UA) 173
5.1.3. Domains and Domain Walls 174
5.1.4. Switching in Thin Films 177
5.2. Applications . . . . . . .. 182
5.2.1. Computer Memories 182
5.2.2. Domain-Motion Devices 187
5.2.3. Thin Film Magnetic Heads 193
5.2.4. Magnetic Displays 196
Chapter 6. Quantum Engineering Applications 199
6.1. Introduction 199
6.2. Basic Concepts . . . . . . . . 199
6.3. Superconductivity in Thin Films 203
6.4. S-N Transition Devices 205
6.4.1. Switching Devices 205
6.4.2. Cryotron Amplifiers 209
6.4.3. Computer Memory Devices 210
6.5. Superconductive Tunneling Devices 215
6.5.1. Quasiparticle (Giaever) Tunneling 215
6.5.2. Pair (Josephson) Tunneling 217
6.5.3. SQUIDs . . . . . . . . . 223
6.5.4. Applications of SQUIDs 225
6.5.5. Superconducting Electronics 227
6.6. Miscellaneous Applications 232
Chapter 7. Thermal Devices .235
7.1. Introduction 235
7.2. Thermal Detectors 236
7.2.1. Bolometers and Thermometers 237
7.2.2. Thermocouples and Thermopiles 240
7.2.3. Pyroelectric Detectors . . . . . 242
7.2.4. Absorption-Edge Thermal Detectors 243
7.3. Thermal Imaging Applications ..... . 244
xii Contents
7.4. Photothermal Conversion 245
7.4.1. Metallic Surfaces . 249
7.4.2. Metal-Semiconductor Tandems 249
7.4.3. Metal-Semiconductor Mixed Coatings 251
7.4.4. Interference Stacks 251
7.4.5. Particulate Coatings 252
7.4.6. Topological Coatings 253
Chapter 8. Surface Engineering Applications .255
8.1. Introduction . . . . . . . . . . 255
8.2. Surface Passivation Applications 257
8.2.1. Coatings of Reaction Product 258
8.2.2. Metallic Coatings . 258
8.2.3. Inorganic Coatings 259
8.2.4. Organic Coatings . 260
8.3. Tribological Applications 260
8.3.1. Wear-Resistant Coatings 261
8.3.2. Lubricating Coatings 265
8.4. Decorative Applications . . . 267
8.5. Miscellaneous Applications 268
8.5.1. Adhesion-Promoting Coatings 268
8.5.2. Preparation of Heterogeneous Catalysts 268
8.5.3. Preparation of Nuclear Fuels . 269
8.5.4. Fabrication of Structural Forms 270
8.5.5. Biomedical Applications 271
References 275
Index 293
