scanning probe microscopies beyond imaging. manipulation of molecules and nanostructures, 2006, p.559

Scanning Probe
Microscopies Beyond
Imaging
Edited by
Paolo Samorı
`
Scanning Probe Microscopies Beyond Imaging. Manipulation of Molecules and Nanostructures.
Edited by Paolo Samorı
`
Copyright 8 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 3-527-31269-2
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Scanning Probe Microscopies Beyond

Imaging
Manipulation of Molecules and Nanostructures
Edited by Paolo Samorı
`
The Editor
Dr. Paolo Samorı
`
Istituto per la Sintesi Organica e la
Fotoreattivita
`
Consiglio Nazionale delle Ricerche
via Gobetti 101
40129 Bologna
Italy
and
Institut de Science et d’Inge
´
nierie
Supramole
´
culaires (ISIS)
Universite
´
Louis Pasteur
8 alle
´
e Gaspard Monge
67083 Strasbourg
France
9 All books published by Wiley-VCH are carefully

produced. Nevertheless, authors, editors, and
publisher do not warrant the information
contained in these books, including this book,
to be free of errors. Readers are advised to keep
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procedural details or other items may
inadvertently be inaccurate.
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A catalogue record for this book is available
from the British Library.
Bibliographic information published by
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Die Deutsche Bibliothek lists this publication in
the Deutsche Nationalbibliografie; detailed
bibliographic data is available in the Internet at
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8 2006 WILEY-VCH Verlag GmbH & Co.
KGaA, Weinheim
All rights reserved (including those of
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ISBN-13: 978-3-527-31269-6
ISBN-10: 3-527-31269-2
To Cristiana
Scanning Probe Microscopies Beyond Imaging. Manipulation of Molecules and Nanostructures.
Edited by Paolo Samorı
`
Copyright 8 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 3-527-31269-2
Foreword
Nanoscience and nanotechnology are interdisciplinary fields involving functional
objects and materials whose components and structures, due to their nanoscale
size, have unusual or enhanced properties. The processing and the manipulation
of complex assemblies on the nanoscale as well as the fabrication of devices with
new sustainable approaches have a paramount importance in view of a technol-
ogy based on intelligent materials. The invention of scanning probe microscopies
(SPMs) truly boosted the development of nanoscience and nanotechnology. SPMs
are key tools for mapping the topography of surfaces as well as for unveiling a va-
riety of physical and chemical properties of molecule-based structures at scales
ranging from hundreds of micrometers down to the subnanometer regime. The
flexibility of their modes makes it possible to single out static and dynamic processes
under different environmental conditions, including gaseous, liquid, and ultra-
high vacuum. Moreover, SPMs allow the manipulation of objects with a nanoscale

precision, thereby making it possible to nanopattern a surface or to elucidate the
nanomechanics of complex artificial and natural assemblies. Thus, they can offer
decisive insight for the optimization of functional nanomaterials and nanodevices.
This book brings together contributions of experts from different fields, with the
aim of casting light on the potential of SPMs to explore as many physico-chemical
properties of single molecules and of larger objects as possible, so as to foster a
greater understanding of surface properties both for unraveling the basic rules
operating at nanoscale level and for the construction of miniaturized devices with
‘‘market potential.’’
This book provides timely summaries of the present status of the applications of
scanning probe microscopies beyond imaging, with a specific emphasis on soft
nanomaterials. The judicious combination of chapters covering technical aspects
of various modes of SPM to gain insight into structural, electrical, and mechanical
properties of nanoscale architectures offers a wide panorama to the reader by high-
lighting stimulating examples of exploitation of these powerful tools. Various
future applications can be foreseen and surely will involve researchers operating
in different disciplines, including physics, chemistry, biology, and materials and
polymer sciences, as well as engineering. The areas that will benefit from these ap-
proaches are countless; among them catalysis, self-assembly of (bio)hybrid archi-
tectures, molecular recognition, and optical, electrical, and mechanical studies of
nanostructures, as well as more technological issues such as nanopatterning, nano-
VII
construction of functional materials, and nanodevice fabrication. Overall, this book
will be a valuable tool for both beginners and more expert scientists interested in
the fascinating realm of scanning probe microscopies and more generally in the
nanoworld.
Jean-Marie Lehn
ISIS-ULP, Strasbourg, France
VIII
Foreword

Scanning Probe Microscopies Beyond Imaging. Manipulation of Molecules and Nanostructures.
Edited by Paolo Samorı
`
Copyright 8 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 3-527-31269-2
Contents
Foreword VII
Preface XIX
List of Authors XXI
I Scanning Tunneling Microscopy-Based Approaches 1
Nanoscale Structural, Mechanical and Electrical Properties 3
1 Chirality in 2D 3
Steven De Feyter and Frans C. De Schryver
1.1 Introduction 3
1.2 Chirality and STM: From 0D to 2D 4
1.2.1 Determination of Absolute Chirality 4
1.2.2 Expression of 2D Chirality by Enantiopure Molecules 6
1.2.3 Racemic Mixture of Chiral Molecules 12
1.2.4 Achiral Molecules 14
1.2.5 Systems with Increased Complexity 21
1.2.6 Multicomponent Systems 23
1.2.6.1 Mixed Systems 23
1.2.6.2 Cocrystals 26
1.2.7 Chemisorption versus Physisorption 26
1.2.8 The Effect of Molecular Adsorption on Substrates: Toward Chiral
Substrates
28
1.2.9 Chirality and AFM 29
1.3 Conclusion 33
Acknowledgements 33

References 33
2 Scanning Tunneling Spectroscopy of Complex Molecular Architectures at
Solid/Liquid Interfaces: Toward Single-Molecule Electronic Devices
36
Frank Ja
¨
ckel and Ju
¨
rgen P. Rabe
2.1 Introduction 36
IX
2.2 STM/STS of Molecular Adsorbates 37
2.3 An Early Example of STS at the Solid/Liquid Interface 38
2.4 Ultrahigh Vacuum versus Solid/Liquid Interface 40
2.5 Probing p-Coupling at the Single-Molecule Level by STS 41
2.6 Molecular Diodes and Prototypical Transistors 47
2.7 Conclusions 51
Acknowledgements 51
References 51
3 Molecular Repositioning to Study Mechanical and Electronic Properties
of Large Molecules
54
Francesca Moresco
3.1 Introduction 54
3.2 Specially Designed Molecules 55
3.3 STM-Induced Manipulation 58
3.3.1 Manipulation of Single Atoms 58
3.3.2 Repositioning of Molecules at Room Temperature 61
3.3.3 Manipulation in Constant Height Mode 61
3.4 Mechanical Properties: Controlled Manipulation of Complex

Molecules
63
3.5 Inducing Conformational Changes: A Route to Molecular Switching
67
3.6 The Role of the Substrate 68
3.7 Electronic Properties: Investigation of the Molecule–Metal Contact 71
3.8 Perspectives 74
Acknowledgements 74
References 74
4 Inelastic Electron Tunneling Microscopy and Spectroscopy of Single Molecules
by STM
77
Jose Ignacio Pascual and Nicola
´
s Lorente
4.1 Introduction 77
4.1.1 Working Principle 78
4.2 Experimental Results 80
4.2.1 C
60
on Ag(110) 82
4.2.2 C
6
H
6
on Ag(110) 85
4.3 Theory 88
4.3.1 Extension of Tersoff–Hamman Theory to IETS–STM 88
4.3.2 Some Model Systems 90
4.3.3 Acetylene Molecules on Cu(100) 90

4.3.4 Oxygen Molecules on Ag(110) 92
4.3.5 Ammonia Molecules on Cu(100) 92
4.4 Conclusion 96
References 96
X
Contents
II Scanning Force Microscopy-Based Approaches 99
Patterning 101
5 Patterning Organic Nanostructures by Scanning Probe Nanolithography 101
Cristiano Albonetti, Rajendra Kshirsagar, Massimiliano Cavallini, and Fabio
Biscarini
5.1 Importance of Patterning Organic Nanostructures 101
5.2 Direct Patterning of Organic Thin Films 102
5.2.1 Fabrication of Nanostructures by a Local Modification 103
5.2.1.1 Nanorecording for Memory Storage 104
5.2.1.2 Local Probe Photolithography 106
5.2.1.3 Nanorubbing 107
5.2.2 Self-Organization of Molecular Nanostructures Triggered by SPM 109
5.3 Assembly of Organic Structures on Nanofabricated Patterns 111
5.3.1 Replacement Nanolithography on Self-Assembly Monolayers
(SAMs)
112
5.3.2 Template Growth of Molecular Nanostructures 114
5.3.2.1 Nanopatterns by Local Oxidation Nanolithography 114
5.3.2.2 Nanopatterns on SAMs 119
5.3.3 Constructive Nanolithography 121
5.3.3.1 Nanolithography by Local Electrochemical Oxidation 122
5.3.3.2 Nanolithography by Local Electrochemical Reduction 124
5.3.3.3 Additional Examples of Patterning by CNL 124
5.3.4 Catalytic Probe Nanolithography 126

5.3.5 Nanografting 128
5.4 Outlook and Conclusions 135
Acknowledgements 136
References 136
6 Dip-Pen Nanolithography 141
Seunghun Hong, Ray Eby, Sung Myung, Byung Yang Lee, Saleem G. Rao, and
Joonkyung Jang
6.1 Introduction 141
6.1.1 History of Writing 141
6.1.2 The Age of Microfabrication 142
6.1.3 New Building Blocks in the Era of Nanotechnology 144
6.2 Basics of Dip-Pen Nanolithography 144
6.2.1 Basic Concepts 144
6.2.2 Ink and Pen 146
6.2.3 DPN Writing Procedure 150
6.3 Lithographic Capability of Dip-Pen Nanolithography 153
6.3.1 Resolution 153
6.3.2 Overcoming Speed Limits via Multiple-Pen Writing 155
Contents
XI
6.3.3 Patterning Extreme Materials: Biomaterials and Conducting
Polymers
157
6.3.4 Unconventional DPN 158
6.3.5 New Pens and Hardware 161
6.4 Other Applications 162
6.4.1 Etching Resist Patterning 162
6.4.2 Nanoassembly 163
6.5 Nanoscale Statistical Physics Inspired by DPN 166
6.5.1 DPN Theory 166

6.5.2 Nanoscale Water Condensation 168
6.5.3 Anomalous Surface Diffusion 170
6.6 Conclusions 170
Acknowledgements 171
References 171
Mechanical Properties 175
7 Scanning Probe Microscopy of Complex Polymer Systems: Beyond Imaging
their Morphology
175
Philippe Leclere, Pascal Viville, Me
´
lanie Jeusette, Jean-Pierre Aime
´
, and Roberto
Lazzaroni
7.1 Introduction 175
7.2 Microscopic Morphologies of Multicomponent Polymer Systems 176
7.3 Methodology 185
7.3.1 Intermittent Contact versus Noncontact Atomic Force Microscopy 185
7.3.2 Modeling the Oscillating Behavior 186
7.3.2.1 Conservative Interaction 186
7.3.2.2 Dissipative Interaction 187
7.3.2.3 Stationary States and Transient States: Error and Phase Signal 192
7.3.2.4 Influence of the Quality Factor upon the Sensitivity 194
7.3.2.5 Approach–Retract Curve (ARC) Analysis 196
7.4 Combined Analysis of Height and Phase Images 198
7.4.1 Pure Topographic Contribution 198
7.4.2 Pure Mechanical Contribution 200
7.4.3 Mixed Contributions 203
7.5 Concluding Remarks 205

Acknowledgements 205
References 205
8 Pulsed Force Mode SFM 208
Alexander Gigler and Othmar Marti
8.1 Introduction 208
8.2 Modes of SPM Operation 208
8.2.1 Static Modes 210
XII
Contents
8.2.1.1 Constant Height Mode 210
8.2.1.2 Constant Deflection Mode 211
8.2.2 Dynamic Modes 211
8.2.2.1 Resonant Modes 212
8.2.2.2 Force Modulation Mode 213
8.2.2.3 Nanoindentations 213
8.3 Pulsed Force Mode 213
8.3.1 Technical Implementation of Pulsed Force Mode 216
8.3.2 Analogies and Differences between PFM, JM, and Force–Volume
Mode
217
8.3.3 Extending PFM to CODYMode for Full Mechanical Characterization of
Samples
217
8.4 Theoretical Description of Contact Mechanics 218
8.4.1 Hertzian Modeling 218
8.4.2 Sneddon’s Extensions to the Hertzian Model 222
8.4.3 Models Incorporating Adhesion 223
8.5 AFM Measurements Using Pulsed Force Mode 227
8.5.1 Force Curves 227
8.5.2 Data Evaluation 229

8.6 Applications of Pulsed Force Mode 233
8.6.1 Examination of Dewetting Polymer Blends 235
8.6.2 Excimer Laser Ablation of PMMA and Adhesion Measurements by
PFM
235
8.6.3 Temperature-Dependent PFM Investigations of Crystalline PTFE 235
8.6.4 Conducting PFM of Lithographically Structured Circuitry 238
8.6.5 Investigation of Very Thin Layers of Poly(vinyl alcohol) in PFM 239
8.6.6 PFM in Liquids with Chemically Modified Tips 239
8.6.7 Electric Double Layer – PFM in Liquids 239
8.6.8 Measuring Biological Samples in Liquids 242
8.6.9 Combined Mechanical Measurements – CODYMode 242
8.7 Conclusions 245
Acknowledgements 246
References 246
9 Force Spectroscopy 250
Phil Williams
9.1 Introduction 250
9.2 Basic Experiments 251
9.3 Theory 252
9.4 The Ramp-of-Force Experiment 255
9.5 Multiple Transition States 258
9.6 Multiple Bonds 258
9.7 Distributions 259
9.8 Simulations 260
9.8.1 An Example: The Streptavidin–Biotin Interaction 263
Contents
XIII
9.9 The Future 266
References 267

Appendix 272
Bond Strength and Tracking Chemical Reactions 275
10 Chemical Force Microscopy: Nanometer-Scale Surface Analysis with Chemical
Sensitivity
275
Holger Scho
¨
nherr and G. Julius Vancso
10.1 Introduction: Mapping of Surface Composition by AFM
Approaches
275
10.2 Chemical Force Microscopy: Basics 277
10.2.1 Surface Modification Procedures for Tip Modification 278
10.2.1.1 Thiol-Based Self-Assembled Monolayers (SAMs) on Gold 278
10.2.1.2 SAMs on Hydroxylated Silicon and Si
3
N
4
280
10.2.1.3 Modified Carbon Nanotube Probes 281
10.2.2 Force Measurements and Mapping in CFM 281
10.2.2.1 Normal Forces 282
10.2.2.2 Lateral Forces 285
10.2.2.3 Intermittent Contact Mode Phase Imaging 285
10.2.3 AFM Using Chemically Modified Tips 286
10.2.3.1 Stability of SAMs and Modified Tips 286
10.2.3.2 Imaging with Optimized Forces 287
10.2.3.3 Distinguishing Different Functional Groups on Surfaces by CFM 287
10.2.3.4 Artifacts and Experimental Difficulties 289
10.3 Applications of CFM 293

10.3.1 Surface Characterization by CFM 293
10.3.1.1 Tip–Sample Forces and Interfacial Free Energies 293
10.3.1.2 Acid–Base Titrations 298
10.3.1.3 Following Surface Chemical Reactions in SAMs 300
10.3.2 Compositional Mapping of Heterogeneous Surfaces 301
10.3.2.1 Micro- and Nanometer-Scale Patterned SAMs 301
10.3.2.2 Heterogeneous and Multiphase Systems 303
10.3.2.3 Surface-Treated Polymers 305
10.4 Outlook 309
Acknowledgements 310
References 310
11 Atomic Force Microscopy-Based Single-Molecule Force Spectroscopy of
Synthetic Supramolecular Dimers and Polymers
315
Shan Zou, Holger Scho
¨
nherr, and G. Julius Vancso
11.1 Introduction 315
11.2 Supramolecular Interactions 318
11.2.1 Hydrogen Bonds 319
XIV
Contents
11.2.2 Coordinative Bonds 321
11.2.3 p-Electron Stacking 322
11.3 AFM-Based Single-Molecule Force Spectroscopy (SMFS) 323
11.3.1 SMFS Experiments 323
11.3.2 Rupture Forces of Molecular Bonds 325
11.3.2.1 Rupture of Single Bonds 325
11.3.2.2 Crossover from Near-Equilibrium to Far-from-Equilibrium Unbinding
and Effect of Soft Polymer Linkages on Strengths

327
11.3.2.3 Rupture of Multiple Bonds 328
11.4 SMFS of Synthetic Supramolecular Dimers and Polymers 330
11.4.1 Host–Guest Interactions in Inclusion Complexes 330
11.4.1.1 b-CD-Based Inclusion Complexes 330
11.4.1.2 Inclusion Complexes of Resorc[4]arene Cavitands 335
11.4.1.3 Inclusion Complexes of Crown Ethers 336
11.4.2 Host–Guest Interactions via H-bonds: Quadruple H-bonded UPy
Complexes
338
11.4.3 Metal-Mediated Coordination Interactions 344
11.4.3.1 Interactions Between Histidine and Nickel Nitrilotriacetate 344
11.4.3.2 Metallo-Supramolecular Ruthenium(II) Complexes 344
11.4.4 Charge-Transfer Complexes 346
11.5 Conclusions and Outlook 347
Acknowledgments 349
References 350
Electrical Properties of Nanoscale Objects 355
12 Electrical Measurements with SFM-Based Techniques 355
Pedro. J. de Pablo and Julio Go
´
mez-Herrero
12.1 Introduction 355
12.2 SFM Tips 358
12.3 Setups for Short Molecules 359
12.4 Experiments with Molecular Wires (MWs) 364
12.4.1 Contact Experiments on Long Molecules 365
12.4.1.1 Contact Experiments in Single-Walled Carbon Nanotubes 366
12.4.1.2 The Influence of Buckling on the Electrical Properties of SWNTs 371
12.4.1.3 Radial Electromechanical Properties of SWNTs 371

12.4.1.4 Three Electrodes plus a Gate Voltage 374
12.4.1.5 Contact Experiments on Single DNA Molecules 374
12.4.1.6 Electrical Maps of SWNTs 376
12.4.1.7 Electrical Maps of V
2
O
5
Nanofibers with Jumping Mode 377
12.4.1.8 Using Tunneling Current to Obtain Current Maps of SWNTs 378
12.5 Noncontact Experiments 379
12.5.1 Carbon Nanotubes 381
12.5.2 Single DNA Molecules 384
References 387
Contents
XV
13 Electronic Characterization of Organic Thin Films by Kelvin Probe Force
Microscopy
390
Vincenzo Palermo, Matteo Palma, and Paolo Samorı
`
13.1 Introduction 390
13.2 Kelvin Probe Scanning Force Microscopy 392
13.3 Interpretation of the Signal in KPFM Measurements 396
13.4 Electronic Characterization of Organic Semiconductors 400
13.5 KPFM of Conventional Inorganic Materials 403
13.6 KPFM on Organic Monolayers, Supramolecular Systems, and Biological
Molecules
407
13.7 KPFM on Organic Electronic Devices 413
13.8 Conclusions and Future Challenges 422

Acknowledgements 422
References 423
Appendix: Practical Aspects of KPFM 426
III Other SPM Methodologies 431
14 Scanning Electrochemical Microscopy Beyond Imaging 433
Franc¸ois O. Laforge and Michael V. Mirkin
14.1 Introduction 433
14.2 SECM Principle of Operation 434
14.2.1 Feedback Mode 434
14.2.2 Tip Generation/Substrate Collection 436
14.2.3 Substrate Generation/Tip Collection Mode 437
14.3 Instrumentation 438
14.3.1 Tip 438
14.3.2 Positioning 439
14.3.3 Potentiostat 439
14.4 Theory 439
14.4.1 Analytical Approximations for Steady-State Responses 440
14.4.1.1 Diffusion-Controlled Heterogeneous Reactions 440
14.4.1.2 Finite Kinetics at the Tip or Substrate 443
14.4.1.3 SG/TC Mode 444
14.5 Applications 445
14.5.1 Heterogeneous Electron Transfer 445
14.5.1.1 Electron Transfer Kinetics at Solid/Liquid Interfaces 445
14.5.1.2 Liquid/Liquid ET Kinetics 447
14.5.2 Experiments Employing Nanoelectrodes 450
14.5.3 Surface Reactions: Corrosion and Dissolution of Ionic Crystals 452
14.5.4 Biological Systems 454
14.5.4.1 Single-Cell Measurements 454
14.5.4.2 Redox Enzymes 456
14.5.5 Surface Patterning 459

XVI
Contents
Acknowledgements 464
References 464
IV Theoretical Approaches 469
15 Theory of Elastic and Inelastic Transport from Tunneling to Contact 471
Nicolas Lorente and Mads Brandbyge
15.1 Introduction 471
15.2 Theory of Tunneling Conductance 472
15.2.1 Introduction 472
15.2.2 Tunneling Calculations with Bardeen’s Transfer Hamiltonian 472
15.2.3 Extension of the Bardeen Approach to the Many-Body Problem 474
15.3 Theory of Inelastic Processes in Electron Transport 475
15.3.1 Linear Model for the Electron–Vibration Coupling 476
15.3.2 Tunneling Regime 477
15.3.2.1 Approaches Based on Scattering Theory 478
15.3.3 Approaches Based on Conductance Calculations 479
15.3.4 Inelastic Approach Based on Bardeen’s Approximation 480
15.4 Elastic High-Transmission Regime 484
15.4.1 The Orbital-Based DFT-NEGF Method 485
15.5 Inelastic High-Transmission Regime 492
15.6 Conclusions and Outlook 497
Acknowledgements 499
References 499
Appendix A 502
Appendix B 504
16 Mechanical Properties of Single Molecules: A Theoretical Approach 508
Pasquale De Santis, Raffaella Paparcone, Maria Savino, and Anita Scipioni
16.1 Introduction 508
16.2 DNA Curvature 509

16.3 DNA Flexibility 511
16.4 The Worm-Like Chain Model 513
16.5 DNA Persistence Length in Two Dimensions 514
16.6 A Model for Predicting the DNA Intrinsic Curvature and
Flexibility
515
16.7 Mapping Sequence-Dependent DNA Curvature and Flexibility from
Microscopy Images
518
16.8 The Ensemble Curvature and the Corresponding Standard Deviation for
a Segmented DNA
519
16.9 The Symmetry of Palindromic DNA Images 521
16.10 Experimental Evidence of DNA Sequence Recognition by Mica
Surfaces
523
Contents
XVII
16.11 Comparison between Theoretical and Experimental DNA Curvature and
Flexibility
525
16.12 Sequence-Dependent DNA Dynamics from SFM Time-Resolved DNA
Images
529
16.13 Conclusions 531
Acknowledgements 532
References 532
Index 534
XVIII
Contents

Scanning Probe Microscopies Beyond Imaging. Manipulation of Molecules and Nanostructures.
Edited by Paolo Samorı
`
Copyright 8 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 3-527-31269-2
Preface
Following the invention of scanning tunneling microscopy (STM), and later of
atomic force microscopy (AFM), in the early 1980s a terrific effort has been ad-
dressed to the study of morphology and structures of surfaces and interfaces. Im-
mediately, very fascinating and artistically excellent images have been generated,
providing a direct view into the nanoworld. Chemists, physicists, and engineers
quickly realized the potential of these techniques and started to bestow more and
more information on nanoscale objects, expanding their researches beyond imag-
ing, thereby exploring physico-chemical properties of matter in a quantitative man-
ner, and triggering actions that can highlight specific characteristics of the molecu-
lar nanosystems under investigation. Such fertile application of scanning probe
microscopies (SPMs) takes great advantage of the unique versatility of these tools.
Moreover, the simplicity in the different modes as well as their applicability to dif-
ferent kinds of samples provides direct access to new realms at the interface
between diverse disciplines, and opens up a vast range of applications that foster
materials science in the nanoscale world.
By bringing together the contributions of pre-eminent scientists operating in the
field, this book aims at providing a wide overview of different applications of SPM
beyond imaging, in particular exploiting STM- and AFM-based approaches, pri-
marily on soft (nano)materials comprising organic, supramolecular, polymeric,
and biological architectures adsorbed on inorganic and metallic surfaces. Particular
attention is paid to fundamental studies on the interactions governing various
nanoscale processes in both biological and artificial supramolecular systems, and
to mechanical and electrical properties of molecules and macromolecules, as well
as to controlled nanopatterning of soft matter. Moreover, STM examples of chirality

in 2D and single-molecule manipulations, as well as STM spectroscopies at
the single-molecule level, are highlighted, enabling unprecedented insight to be
gained into individual nano-entities. Most importantly, as highlighted in this
book, nowadays there are already quite a few groups employing SPM beyond imag-
ing; nevertheless this field is still in its infancy. New applications can be envisioned
which surely will be boosted by the implementation of new SPM modes.
I would like to acknowledge all the colleagues who enthusiastically contributed
to this book. I am grateful to Martin Ottmar and Eva E. Wille for their invitation
to edit this book, and to Waltraud Wu
¨
st, who has been working closely with me to
XIX
make it a reality. Finally I am thankful to Jean-Marie Lehn for his support in writ-
ing the foreword.
ISOF-CNR Bologna Paolo Samorı
`
Italy & ISIS-ULP
Strasbourg, France
XX
Preface
List of Authors
Jean-Pierre Aime
´
CPMOH, Universite
´
de Bordeaux I
351 Cours de la Libe
´
ration
33405 Talence ce

´
dex
France
Cristiano Albonetti
CNR – Istituto per lo Studio dei Materiali
Nanostrutturati (ISMN)
Via P. Gobetti 101
40129 Bologna
Italy
Fabio Biscarini
CNR – Istituto per lo Studio dei Materiali
Nanostrutturati (ISMN)
Via P. Gobetti 101
40129 Bologna
Italy
Mads Brandbyge
Department of Micro and Nanotechnology
Technical University of Denmark
Ørsteds Plads, Bldg. 345E
2800 Lyngby
Denmark
Massimiliano Cavallini
CNR – Istituto per lo Studio dei Materiali
Nanostrutturati (ISMN)
Via P. Gobetti 101
40129 Bologna
Italy
Steven De Feyter
Katholieke Universiteit Leuven
Department of Chemistry

Celestijnenlaan 200 F
3001 Leuven
Belgium
Pasquale De Santis
Dipartimento di Chimica
Universita
`
di Roma ‘‘La Sapienza’’
P. le A. Moro 5
00185 Roma
Italy
Frans C. De Schryver
Katholieke Universiteit Leuven
Department of Chemistry
Celestijnenlaan 200 F
3001 Leuven
Belgium
Ray Eby
NanoInk
Inc. 215 E. Hacienda Avenue
Campbell
CA 95008
USA
Alexander Gigler
Department of Experimental Physics
University Ulm
89069 Ulm
Germany
Julio Go
´

mez-Herrero
Departamento de Fı
´
sica de la Materia
Condensada C-III
Universidad Auto
´
noma de Madrid
28049 Madrid
Spain
Seunghun Hong
Physics and NANO Systems Institute
Seoul National University
San 56-1
Sillim-dong
Kwanak-gu
Seoul 151-747
Korea
XXI
Frank Ja
¨
ckel
Department of Physics
Humboldt University Berlin
Newtonstr. 15
12489 Berlin
Germany
Joonkyung Jang
School of Nano Science and Technology
Pusan National University

San 30
Jangjeon-dong
Geumjeong-gu
Busan 609-735
Korea
Me
´
lanie Jeusette
Service de Chimie des Mate
´
riaux Nouveaux
Materia Nova/Universite
´
de Mons-Hainaut
Place du Parc 20
7000 Mons
Belgium
Rajendra Kshirsagar
CNR – Istituto per lo Studio dei Materiali
Nanostrutturati (ISMN)
Via P. Gobetti 101
40129 Bologna
Italy
Franc¸ois O. Laforge
Department of Chemistry & Biochemistry
Queens College– CUNY
Flushing, NY 11367
USA
Roberto Lazzaroni
Service de Chimie des Mate

´
riaux Nouveaux
Materia Nova/Universite
´
de Mons-Hainaut
Place du Parc 20
7000 Mons
Belgium
Philippe Leclere
Service de Chimie des Mate
´
riaux Nouveaux
Materia Nova/Universite
´
de Mons-Hainaut
Place du Parc 20
7000 Mons
Belgium
Byung Yang Lee
School of Physics
Seoul National University
San 56-1
Sillim-dong
Kwanak-gu
Seoul 151-747
Korea
Nicola
´
s Lorente
Laboratoire Collisions

Agre
´
gats, Re
´
activite
´
UMR5589, Universite
´
Paul Sabatier
118 route de Narbonne
31062 Toulouse ce
´
dex 4
France
Othmar Marti
Department of Experimental Physics
University Ulm
89069 Ulm
Germany
Michael V. Mirkin
Department of Chemistry & Biochemistry
Queens College– CUNY
Flushing, NY 11367
USA
Francesca Moresco
Institut fu
¨
r Experimentalphysik
Freie Universita
¨

t Berlin
Arnimallee 14
14195 Berlin
Germany
Sung Myung
School of Physics
Seoul National University
San 56-1
Sillim-dong
Kwanak-gu Seoul 151-747
Korea
Pedro J. de Pablo
Departamento de Fı
´
sica de la Materia
Condensada C-III
Universidad Auto
´
noma de Madrid
28049 Madrid
Spain
Vincenzo Palermo
Istituto per la Sintesi Organica e la
Fotoreattivita
`
Consiglio Nazionale delle Ricerche
via Gobetti 101
40129 Bologna
Italy
Matteo Palma

Institut de Science et d’Inge
´
nierie
Supramole
´
culaires (ISIS)
Universite
´
Louis Pasteur
8 alle
´
e Gaspard Monge
67083 Strasbourg
France
XXII
List of Authors
Raffaella Paparcone
Dipartimento di Chimica
Universita
`
di Roma ‘‘La Sapienza’’
P. le A. Moro 5
00185 Roma
Italy
Jose
´
I. Pascual
Institut fu
¨
r Experimentalphysik

Freie Universita
¨
t Berlin
Arnimallee 14
14195 Berlin
Germany
Ju
¨
rgen P. Rabe
Department of Physics
Humboldt University Berlin
Newtonstr. 15
12489 Berlin
Germany
Saleem G. Rao
Department of Physics
Florida State University
315 Keen Building
Tallahassee
FL 32306
USA
Paolo Samorı
`
Istituto per la Sintesi Organica e la
Fotoreattivita
`
–
Consiglio Nazionale delle Ricerche
via Gobetti 101
40129 Bologna

Italy
and
Institut de Science et d’Inge
´
nierie
Supramole
´
culaires (ISIS)
Universite
´
Louis Pasteur
8 alle
´
e Gaspard Monge
67083 Strasbourg
France
Maria Savino
Dipartimento di Genetica e Biologia
Molecolare
Fondazione Pasteur-Cenci Bolognetti
Universita
`
di Roma ‘‘La Sapienza’’
P. le A. Moro 5
00185 Roma
Italy
Holger Scho
¨
nherr
University of Twente

MESA
þ
Institute for Nanotechnology and
Faculty of Science and Technology
Department of Materials Science and
Technology of Polymers
7500 AE Enschede
The Netherlands
Anita Scipioni
Dipartimento di Chimica
Universita
`
di Roma ‘‘La Sapienza’’
P. le A. Moro 5
00185 Roma
Italy
G. Julius Vancso
University of Twente
MESA
þ
Institute for Nanotechnology and
Faculty of Science and Technology
Department of Materials Science and
Technology of Polymers
7500 AE Enschede
The Netherlands
Pascal Viville
Service de Chimie des Mate
´
riaux Nouveaux

Materia Nova/Universite
´
de Mons-Hainaut
Place du Parc 20
7000 Mons
Belgium
Phil Williams
Laboratory of Biophysics and Surface Analysis
School of Pharmacy
University of Nottingham
Nottingham NG7 2RD
UK
Shan Zou
MESA
þ
Institute for Nanotechnology and
Materials Science and Technology of Polymers
University of Twente
7500 AE Enschede
The Netherlands
List of Authors
XXIII
Part I
Scanning Tunneling Microscopy-Based
Approaches
Scanning Probe Microscopies Beyond Imaging. Manipulation of Molecules and Nanostructures.
Edited by Paolo Samorı
`
Copyright 8 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 3-527-31269-2

Nanoscale Structural, Mechanical and
Electrical Properties
1
Chirality in 2D
Steven De Feyter and Frans C. De Schryver
1.1
Introduction
The existence and induction of chirality are among the most intriguing and inspir-
ing phenomena in nature. Chirality can be defined as a geometric property which
dictates that an object and its mirror image are non-superimposable by any trans-
lation or rotation. A chiral object therefore has no inverse symmetry elements (i.e.,
center of inversion or reflection planes). In fact, it is easier to create chirality in two
dimensions than in three: a surface does not have a center of inversion, and reflec-
tion mirror symmetry is only allowed normal to the surface [1–3]. In many cases
even the simple adsorption of a single molecule, chiral or achiral, on a substrate
leads to the formation of a chiral entity. Often, its two-dimensional self-assembled
structures are chiral too.
One of the main reasons why this particular field of research, expression of chir-
ality at surfaces, has only been burgeoning in the last couple of years is the diffi-
culty in evaluating the chiral nature of molecules on surfaces. In Langmuir and
Langmuir–Blodgett films, pressure–area isotherms and epifluorescence micros-
copy were traditionally used to evaluate 2D chirality. However, these techniques
do not provide direct insight into the molecular interactions at play. With grazing
incidence X-ray diffraction measurements one can achieve information on the or-
dering of the molecules with near-atomic resolution though, as this is a diffraction
technique, data are averaged over a macroscale area [4].
The ability of scanning probe microscopy techniques to investigate the adsorp-
tion and ordering of single molecules, clusters, fibers, and complete monolayers,
both under UHV and ambient conditions, and at the liquid/solid interface has
stimulated the activities in this particular field of research. Expression of chirality

upon adsorption can be evaluated, ranging from the submolecular level to ex-
tended monolayers. The level of detail these techniques are able to reveal is amaz-
ing and over the last few years a wealth of data has been gathered.
3