Langmuir-Blodgett Films

435 Pages·1990·13.557 MB·English

by  C. H. Giles, S. D. Forrester, G. G. Roberts (auth.), Gareth Roberts (eds.)

Langmuir-Blodgett
Films
Langmuir-Blodgett
Films
Edited by
GARETH RoBERTS
Thorn EM/ pic
Hayes, Middlesex, United Kingdom
and University of Oxford
Oxford, United Kingdom
Springer Science+Business Media, LLC
Library of Congress Catalog1ng-1n-Publ1cat1on Data
Langmuir-Blodgett films I edited by Gareth Roberts.
p. em.
Includes bibliographical references.
ISBN 0-308-43318-8
1. Thin films, Multilayered. 2. Monomolecular fil•s.
I. Roberts, G. G. <Gareth Gwyn>, 1940-
QC178.9.M84L38 1990
821.381'52--dc20 89-72111
CIP
ISBN 978-1-4899-3718-6 ISBN 978-1-4899-3716-2 (eBook)
DOI 10.1007/978-1-4899-3716-2
© 1990 Springer Science+Business Media New York
Originally published by Plenum Press, New York in 1990.
Softcover reprint of the hardcover 1st edition 1990
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
Contributors
W. A. Barlow, Electronics Group, Imperial Chemical Industries plc, Runcom,
Cheshire WA 7 4QE, England
S.D. Forrester, Department of Pure and Applied Chemistry, University of Strath
clyde, Glasgow, Scotland
tC. H. Giles, Department of Pure and Applied Chemistry, University of Strath
clyde, Glasgow, Scotland
R. A. Hann, ICI Imagedata, Brantham, Manningtree, Essex COil INL, England
D. Mobius, Max Planck Institute for Biophysical Chemistry (Karl-Freidrich
Bonhoeffer Institute), D-3400 Gottingen-Nikolausberg, Federal Republic of
Germany
M. C. Pedy, Molecular Electronics Research Group, School of Engineering and
Applied Science, University of Durham, Durham DHI 3LE, England
G. G. Roberts, Department of Engineering Science, University of Oxford, Oxford
OXI 3PJ, England, and Thorn EMI plc, Hayes, Middlesex UB3 IHH, England
R. M. Swart, Corporate Colloid Science Laboratory, Imperial Chemical Industries
plc, Runcom, Cheshire WA7 4QE, England
tDeceased.
v
Preface
Monomolecular assemblies on substrates, now termed Langmuir-Blodgett (LB)
films, have been studied for over half a century. Their development can be viewed in
three stages. Following the pioneering work of Irving Langmuir and Katharine
Blodgett in the late 1930s there was a brief flurry of activity just before and just after
the Second World War. Many years later Hans Kuhn published his stimulating work
on energy transfer. This German contribution to the field, made in the mid-1960s,
can be regarded as laying the foundation for studies of artificial systems of cooperat
ing molecules on solid substrates. However, the resurgence of activity in academic
and industrial laboratories, which has resulted in four large international con
ferences, would not have occurred but for British and French groups highlighting
the possible applications of LB films in thefield of electronics.
Many academic and industrial establishments involved in high technology are
now active in or maintaining a watching brief on the field. Nevertheless this impor
tant area of solid state science is still perhaps largely unfamiliar to many involved in
materials or electronic device research. The richness of the variety of organic
molecular materials suitable for LB film deposition offers enormous scope for those
interested in their basic properties or their practical applications.
LB films are now an integral part of the field of molecular electronics. It seems
inevitable that they will play some role in replacing inorganic materials in certain
areas of application. Enthusiasts believe that a further stage will be reached with
supermolecular assemblies in which entirely novel effects are discovered, and these
findings in tum will lead to the fabrication of novel devices operating at the
nanometer scale for the processing of information and its transmission and storage.
This book, which consists of contributions from leading research workers, is
intended to impart to this broad audience and students new to the field a firm
grounding in the subject. All aspects of this truly interdisciplinary and multi
disciplinary subject are covered, from a historical introduction to a concluding
vii
viii Preface
chapter describing the potential applications of LB films. Each chapter is more or
less independent of the others and each author has been encouraged to write in his
own style. Therefore omissions and variations in the level of treatment are inevita
ble. Unfortunately, the pace of research in the field will have made the references in
some chapters representative rather than exhaustive. We apologize to those whose
recent work is not cited and would direct readers to the proceedings of the 1989
International Conference.
In the course of writing, many research colleagues have provided assistance.
The authors wish to acknowledge this support and also wish to thank Mrs. Frances
Greenwood and Mrs. Pauline Morrell for their assistance with the preparation of the
manuscript.
Gareth Roberts
Hayes and Oxford
Contents
Chapter 1
Historical Introduction
C. H. Giles, S. D. Forrester, and G. G. Roberts
1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2. Early Contributors to the Field of Monolayer Science . . . . . . . . . . . . . . 2
1.2.1. Franklin (1706-1790) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.2. Shields (1822-1890) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.3. Aitken (1839-1919) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.4. Rayleigh (1842-1919) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.5. Pockels (1862-1935) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.6. Langmuir (1881-1957) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.2.7. Blodgett(1898-1979).................................. 11
1.3. Conclusion........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Chapter 2
Molecular Structure and Monolayer Properties
R. A. Hann
2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2. Formation and Stability of Monolayers . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2. 2 .1. Surface Pressure/ Area Isotherms . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.2. Modeling Molecular Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.3. Other Properties of Langmuir Films . . . . . . . . . . . . . . . . . . . . . . 25
2.2.4. Mixed Monolayers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
lx
X Contents
2.3. Langmuir-Blodgett Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.4. Types of Molecules Known to Form Monolayers and Langmuir-
Blodgett Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.4.1. Fatty Acids and Their Derivatives . . . . . . . . . . . . . . . . . . . . . . . . 32
2.4.1.1. Chemical Structure of Fatty Acids . . . . . . . . . . . . . . . . 32
2.4.1.2. Incorporation of Metal Ions . . . . . . . . . . . . . . . . . . . . . 33
2.4.1.3. Fatty Acids with Modified Hydrophobic Tailgroups . . 35
2.4.1.4. Modifications to the Hydrophilic Headgroup . . . . . . . . 41
2.4.2. Molecules Containing Five- or Six-Membered Rings . . . . . . . . . 45
2.4.2.1. Derivatives of Benzene . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.4.2.2. Derivatives of Polycyclic Aromatic Hydrocarbons . . . 46
2.4.2.3. Heterocyclic Compounds and Dyes . . . . . . . . . . . . . . . 53
2.4.3. Porphyrins and Phthalocyanines . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.4.4. Mixed Monolayers of Unsubstituted Hydrophobic Materials . . . 67
2.5. Polymers and Polymerizable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . 68
2.5.1. Preformed Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
2.5.2. Polymers Formed in situ by Addition of Carbon-Carbon
Double Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.5.3. Diacetylenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
2.5.4. Oxirans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.5.5. Condensation Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.5.6. Opportu,nities for New Materials . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.6. Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
2.6.1. Non-Langmuir-Blodgett Multilayers . . . . . . . . . . . . . . . . . . . . . . 79
2.6.2. Nonaqueous Subphases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
2. 7. Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
2.8. Postscript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Chapter 3
Film Deposition
M. C. Petty and W. A. Barlow
3.1. Deposition Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
3.2. Subphase and Containment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
3. 3. Compression Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3.3.1. Single Movable Barrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3.3.2. Circular Trough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
3.3.3. Constant Perimeter Barrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
3.4. Ancillary Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
3.4.1. Surface Pressure Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
3.4.2. Surface Area Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.4.3. Deposition Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Contents xi
3.4.4. Control Systems ...................................... 110
3.5. Trough Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.6. Experimental Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
3.6.1. Surface Cleaning ...................................... 113
3.6.2. Monolayer Spreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
3.6.3. Substrate Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
3.6.4. Monolayer Transfer .................................... 118
3.7. Other Systems .............................................. 120
3.7.1. Continuous Fabrication ................................. 120
3.7.2. Alternate-Layer Troughs ................................ 122
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Chapter 4
Characterization and Properties
M. C. Petty
4.1. Introduction ................................................ 133
4.2. Evaluation of Film Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
4.2.1. Interference Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
4.2.2. Ellipsometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
4.2.3. X-Ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
4.2.4. Neutron Diffraction and Reflection . . . . . . . . . . . . . . . . . . . . . . . 140
4.2.5. Alternative Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.3. Film Structure . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.3.1. Electron Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.3.2. Optical Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
4.3.3. IR and Visible Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
4.3.4. Raman Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
4.3.5. Surface Analytical Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
4.3.6. Other Characterization Methods .......................... 160
4.4. Optical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
4.4.1. Refractive Index ...................................... 162
4.4.2. Nonlinear Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
4.5. Electrical Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
4.5.1. Specimen Preparation .................................. 167
4.5.2. Quantum Mechanical Tunneling .......................... 169
4.5.3. Direct Current Conduction through Multilayers ............ 175
4.5.4. Conductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
4.5.5. Permittivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
4.5.6. Permanent Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
4.5.7. Dielectric Breakdown .................................. 192
4.6. Other Phenomena ........................................... 193
4.6.1. Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193