3169 boekomslag • def [XP] 23-09-1998 11:55 Pagina 1 Nanotechnology is considered a key technology for the 21st century NanotechnologyNanotechnology by renowned scientists. But what Towards a molecular construction kit exactly is nanotechnology? What is Towards a molecular construction kit the difference between ‘bottom-up’ and ‘top-down’ nanofabrication, and what is a scanning probe micro- scope? And most of all: what will nanotechnology bring us? These questions are addressed in Edited by Arthur ten Wolde this book from the Netherlands Study Centre for Technology Trends (STT). It uses terms that are understandable to a wide technically interested audience. It provides an overview of STT 60 the scientific state of the art as well as the technological potential of nanomaterials, nanoelectronics, molecular nanotechnology and nano- scale-resolution microscopes. The impact is illustrated with examples of current and future applications in almost every product area. This book is a special jubilee edition to celebrate STT’s 30th anniversary. It is the tangible result of a collaborative effort from STT and many scientists from universities and industry with backgrounds in physics, chemistry and biology. This publication is intended for everyone involved in technological development, and especially for ISBN 90-804496-1-X those interested in this wave of innovation surpassing the impact of information technology and biotechnology. 9 789080 449619 Nanotechnology The Netherlands Study Centre for Technology Trends (STT), founded in 1968 by the Royal Institution of Engineers in the Netherlands, has the following aims: – to evaluate technological trends from the viewpoint of the engineering sciences and to explore their interaction with other developments in society as a whole; – to give wide publicity to its findings as a contribution to a more integrated picture of the future of society in the Netherlands and elsewhere. STT addresses itself to industry, government, science, and the interested layman. STT is established at Prinsessegracht 23, The Hague. Correspondence address: P.O. Box 30424, 2500 GK The Hague, The Netherlands. Telephone: +31 70 3919855. Nanotechnology Towards a molecular construction kit Edited by Arthur ten Wolde 1998 Netherlands Study Centre for Technology Trends (STT) The Hague, The Netherlands American science editor Yvonne Carts-Powell Book design Salabim Design Consultancy BNO, Rotterdam Illustrations Johan Manschot Jerry den Ambtman J. ten Hove Printing Macula, Boskoop CIP-DATA KONINKLIJKE BIBLIOTHEEK, DEN HAAG ISBN 90-804496-1-X NUGI 841 © 1998 Stichting Toekomstbeeld der Techniek, Den Haag All rights reserved under international copyright conventions. No part of this work may be reproduced in any form by print, photoprint, microfilm or any other means without written permission from the publisher. Inquiries to Stichting Reprorecht Amstelveen, The Netherlands. Contents 6 Bottom up! 10 Samenvatting 12 Executive summary 20 1. Introduction 1.1 What is nanotechnology? 28 1.2 Recent breakthroughs in nanotechnology 37 1.3 International situation 42 1.3.1 Other nanotechnology foresight studies 42 1.3.2 Nanotechnology in Europe 43 1.3.3 Nanotechnology in Japan 47 1.3.4 Nanotechnology research in the USA 49 1.3.5 International comparison 53 1.4 About this book 56 2. Nanoelectronics 2.1 Introduction 62 2.2 Nanolithography 63 2.2.1 Nanolithography for integrated-circuit production 63 2.2.2 Microcontact printing 75 2.2.3 Atom lithography 80 2.2.4 Scanning probe nanofabrication 84 2.2.5 Resists for deep-ultraviolet radiation 97 2.2.6 Resists for electron-beam lithography 100 2.2.7 Limitations of dry etching 103 2.2.8 Conclusion 109 2.3 Quantum structures fabricated by epitaxial growth 110 2.4 Nanostructured magnetic memories 116 2.5 Quantum phenomena in nanoscale structures 121 2.6 Novel designs 128 2.7 Outlook 136 3. Nanomaterials 3.1 Introduction 146 3.2 Materials 149 3.2.1 Nanostructured ceramics 149 3.2.2 Nanostructured semiconductor thin films 153 3.2.3 Metal nanoparticles 158 7 3.3 Composites: hybrid coatings 163 3.4 Colloidal dispersions 171 3.5 Synthesis of nanoparticles 179 3.5.1 Gas-phase synthesis 179 3.5.2 Liquid atomization 186 3.6 Characterization by high-resolution transmission electron microscopy 187 3.7 Consolidation: deposition of nanostructured films 190 3.8 Polymer chemistry 197 3.9 Health hazards of nanoparticles 199 3.10 Present and future applications 200 3.11 Opportunities and challenges 207 4. Molecular nanotechnology 4.1 Introduction 216 4.2 Synthesis of nanostructures by self-assembly 218 4.3 Nanostructures through coordination chemistry 225 4.4 Biomineralization as a concept for materials engineering 230 4.5 Nanostructures from surfactant molecules 232 4.6 Medical application: drug and DNA encapsulation 234 4.7 Dendrimers 238 4.8 Transistors based on organic molecules 245 4.9 Molecular solar cells 247 4.10 Computational nanotechnology 252 4.11 Proteins: a source of inspiration 257 4.12 Nanodevices from photobiological materials 265 4.13 The early events in photosynthesis 272 4.14 DNA nanostructures 277 4.15 Prospects for applications 278 4.16 Future prospects 281 5. Nanoscale-resolution microscopes 5.1 Introduction 288 5.2 Scanning tunneling microscopy 289 5.2.1 Principle of operation 289 5.2.2 Instrumental diversification 292 5.2.3 Manipulation versus imaging 297 5.2.4 Conclusion 299 8 5.3 Atomic force microscopy 300 5.3.1 Atomic force microscope technology 300 5.3.2 Chemically specific atomic force microscopy 304 5.3.3 Atomic force microscopy to measure specific molecular interactions in cell biology 305 5.4 Nanometer-resolution optical microscopy 308 5.4.1 Far-field optical microscopes 308 5.4.2 Scanning near-field optical microscopy 313 5.5 Applications 321 5.5.1 The scanning probe industry 321 5.5.2 Current applications of scanning probes 322 5.5.3 Future impact 324 5.6 Window to the nanoworld 329 6. Conclusions and recommendations 332 Appendix 1 Report of the workshop ‘Industrial applications of nanotechnology’ 334 Appendix 2 Applications 338 Appendix 3 Periodic table of elements 340 Survey organization 342 STT Publications 346 Financial support STT 352 Index 354 9 Bottom up! A previous publication of the Netherlands Study Center for Technology Trends (STT) ‘Microsystem technology: exploring opportunities’ (1994) argued that the miniaturization of electromechanical systems combined with several conven- tional physical and chemical technologies offers major opportunities for new products and processes. And indeed it does! Now, only a few years later, the size of experimentally manufactured microstructures is becoming so extremely small that a fundamental limit becomes relevant: the size of a single atom. Nanotechnology is concerned with manufacturing on the scale of molecules and atoms, a thousand times smaller than microsystems! This may lead to funda- mentally new properties of materials. Over the next two decades, continued top-down mini-micro-nano-aturization will therefore result in even more (a thousand times more?) opportunities in information technology hardware: the chip of the 21st century is a nanochip. However, making things smaller and smaller is a path that becomes increasingly difficult to follow, full of potholes and roadblocks. The question then arises whether in the distant future, it might be feasible to construct a chip bottom-up from individual atoms and molecules using some kind of ‘molecular construction kit’. Believe it or not, such a construction kit is under development. Chemists are capable of synthesizing nanoparticles, ‘large’ and complex molecules, and assemblies from these molecules. These are the building blocks for future man- ufacturing. Physicists have developed needle devices that can move and sense individual atoms. Together with advanced synthesis, these are to be the tools of future manufacturing. Biologists are learning rapidly how nature accomplishes a variety of astonishing feats, such as growing a molecular motor that propels a bacterium through the water. The combination of such knowledge with the novel tools and building blocks fuels a new manufacturing technology that surpasses 10 Bottom up! both information technology and biotechnology. Nanotechnology is building nature’s way. A completely new manufacturing approach could evolve. To this vision of future manufacturing I raise my glass and say: Bottom up! Thanks to the enthusiasm of a large number of experts from the world of research and industry, both in the Netherlands, Flanders and abroad, STT has succeeded in surveying the most important fields of nanoscale science and technology today. It draws a picture of what the technology can offer us in the future and what needs to be done. The book is thus a good starting-point for building an acquaintance with these developments in the field of nano- technology and gaining insight into the opportunities that it can offer. I hope it will generate ideas which will ultimately contribute to sustainable economic development. Ir.drs. H.N.J. Smits Member of the Executive Board of Rabobank Nederland Chairman of STT The Netherlands 11 Samenvatting Arthur ten Wolde Vraagstelling Nano betekent klein. De term staat voor ‘een miljardste’, en is geïnspireerd op het Oudgriekse woord voor dwerg, ‘nanos’. Nanotechnologie staat voor het bestuderen en manipuleren van piepkleine voorwerpen. De ‘nanowereld’ wordt bevolkt door atomen, moleculen, en moleculaire machines zoals het ribosoom, een cellulair orgaan dat eiwitten aanmaakt. Om een indruk te geven van de nanoschaal: in 1 nanometer (nm) – een miljardste van een meter – passen 6 koolstofatomen op een rij. In de STT-studie werden de volgende vragen gesteld: wat is nanotechnologie precies, en wat voor kansen biedt het? 12 Wat is nanotechnologie? Nanotechnologie is een opkomend veld van onderzoek en ontwikkeling gericht op toenemende controle over materiële structuren met afmetingen op nano- schaal (0,1 tot 100 nm) in tenminste een dimensie. Nanotechnologie is ook een cluster van opkomende technieken uit de vaste-stoftechnologie, biotechnolo- gie, chemische technologie en raster-sondetechnologie, die ‘top-down’ en ‘bot- tom-up’ convergeren naar de nanoschaal.