Cuniberti / Fagas / Richter Introducing Molecular Electronics

1. Auflage 2006
ISBN: 978-3-540-31514-8
Verlag: Springer Berlin Heidelberg
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 680, 537 Seiten

Reihe: Lecture Notes in Physics

This volume presents a summary of our current understanding of molecular electronics combined with selected state-of-the-art results at a level accessible to the advanced undergraduate or novice postgraduate. This single book comprises the basic knowledge of both theory and experiment underpinning this rapidly growing field. Concepts and techniques, such as density functional theory and charge transport, break junctions and scanning probe microscopy are introduced step-by-step and are subsequently used in specific examples. The text addresses a wide range of systems, including molecular junctions made of single-molecules, self-assembled monolayers, carbon nanotubes and DNA.

Autoren/Hrsg.

Cuniberti, Gianaurelio

Fagas, Giorgos

Richter, Klaus

Inhaltsverzeichnis

1;Foreword;6
2;Preface;8
3;Contents;10
4;List of Contributors;16
5;Introducing Molecular Electronics: A Brief Overview;21
5.1;1 A Passage Through Time: Past, Present and Future Challenges;21
5.2;2 What You Find in the Book – a Passage Through Its Contents;24
5.3;3 What is not Included in the Book – Literature Hints;26
5.4;Acknowledgements;28
5.5;References;28
6;Part I Theory;31
6.1;Foundations of Molecular Electronics – Charge Transport in Molecular Conduction Junctions;33
6.1.1;1 Prologue;33
6.1.2;2 Theoretical Approaches to Conductance;38
6.1.3;3 The Relationship Between Electron Transfer Rates and Molecular Conduction;41
6.1.4;4 Interaction with Nuclear Degrees of Freedom;42
6.1.4.1;4.1 Timescale Issues;43
6.1.4.2;4.2 Transition from Coherent to Incoherent Motion;44
6.1.4.3;4.3 Heating and Heat Conduction;47
6.1.4.4;4.4 Inelastic Electron Tunneling Spectroscopy (IETS);51
6.1.5;5 Remarks and Generalities;53
6.1.5.1;5.1 Electron Transfer and Conductance: Common Issues;53
6.1.5.2;5.2 Junction Conductance;54
6.1.6;Acknowledgements;64
6.1.7;References;65
6.2;AC-Driven Transport Through Molecular Wires;75
6.2.1;1 Introduction;75
6.2.2;2 Basic Concepts;76
6.2.2.1;2.1 Model for Driven Molecular Wire Coupled to Leads;76
6.2.2.2;2.2 Current Through Static Molecular Wire;78
6.2.3;3 Floquet Approach to the Driven Transport Problem;79
6.2.3.1;3.1 Retarded Green Function;80
6.2.3.2;3.2 Current Through the Driven Molecular Wire;81
6.2.4;4 Weak-Coupling Approximations;85
6.2.4.1;4.1 Asymptotic Weak Coupling;85
6.2.4.2;4.2 Master-Equation Approach;86
6.2.5;5 Photon-Assisted Transport Across a Molecular Bridge;90
6.2.6;6 Conclusions;92
6.2.7;Acknowledgements;93
6.2.8;References;93
6.3;Electronic Structure Calculations for Nanomolecular Systems;97
6.3.1;1 Electronic Structure of Nanomolecular Systems;97
6.3.2;2 Selected Applications of Ground-State Electronic Structure Calculations by DFT;99
6.3.2.1;2.1 Carbon Nanotubes;100
6.3.2.2;2.2 Model and Realistic DNA-Base Stacks;103
6.3.3;3 Linear Response by TDDFT;108
6.3.3.1;3.1 Excitation Energies in TDDFT;109
6.3.3.2;3.2 Comments;112
6.3.3.3;3.3 Selected Applications of TDDFT;113
6.3.4;4 Wannier Functions for Electronic Structure Calculations;117
6.3.4.1;4.1 Selected Applications of Wannier Computationin Nanostructures;118
6.3.5;Acknowledgements;126
6.3.6;References;127
6.4;Ab-initio Non-Equilibrium Green’s Function Formalism for Calculating Electron Transport in Molecular Devices;137
6.4.1;1 Introduction;137
6.4.2;2 Mean Field Electronic Structure Theory;138
6.4.3;3 Application of DFT to Modeling Molecular Electronics Devices;140
6.4.3.1;3.1 The Screening Approximation;142
6.4.3.2;3.2 Calculating the Charge Density Using Green’s Functions;144
6.4.3.3;3.3 Taking into Account the Electrode Region Through a Self Energy;146
6.4.3.4;3.4 Calculation of the Electrode Green’s Function;147
6.4.3.5;3.5 Integrating the Spectral Density with a Complex Contour;148
6.4.3.6;3.6 Non-Equilibrium Green’s Functions for Finite Bias;148
6.4.3.7;3.7 Calculating the Effective Potential from the Electron Density;150
6.4.3.8;3.8 The Complete Self-Consistent Algorithm for the NEGF Calculation;151
6.4.3.9;3.9 Electron Transport Coe.cients and Currents Obtained from the Green’s Function;153
6.4.4;4 Implementation: McDCAL, TranSIESTA, and Atomistix Virtual NanoLab;154
6.4.5;5 Resistance of Molecular Wires;155
6.4.6;6 Non-Equilibrium Forces;161
6.4.7;7 Conclusion;167
6.4.8;References;167
6.5;Tight-Binding DFT for Molecular Electronics (gDFTB);173
6.5.1;1 Introduction;173
6.5.2;2 The Self-Consistent Density-Functional Tight-Binding;175
6.5.3;3 Setup of the Transport Problem;177
6.5.4;4 The Green’s Function Technique;179
6.5.5;5 The Relationship with the Keldysh Green’s Functions;180
6.5.6;6 The Terminal Currents;183
6.5.7;7 The Poisson Equation;184
6.5.8;8 Atomic Forces;185
6.5.9;9 gDFTB Example Applications;187
6.5.10;10 Incoherent Electron-Phonon Scattering;189
6.5.11;11 Comments on DFT Applied to Transport;199
6.5.12;12 Conclusions;200
6.5.13;References;201
6.6;Current-Induced Effects in Nanoscale Conductors;205
6.6.1;1 Current Through a Nanoscale Junction;205
6.6.2;2 Current-Induced Forces;208
6.6.3;3 Shot Noise;210
6.6.4;4 Local Heating;214
6.6.5;5 Inelastic Conductance;220
6.6.6;6 Conclusions;222
6.6.7;Acknowledgements;222
6.6.8;References;222
6.7;Single Electron Tunneling in Small Molecules;227
6.7.1;1 Introduction;227
6.7.2;2 Tunneling Transport;228
6.7.2.1;2.1 Current and Shot-Noise Spectroscopy;228
6.7.2.2;2.2 Master Equations Current and Shot-Noise;230
6.7.3;3 Electronic Excitations of a Benzene Ring;233
6.7.4;4 Spin Excitations of a [2 × 2] Grid Molecule;235
6.7.5;5 Vibrational Excitations and Multiple Orbitals;239
6.7.6;6 Current Noise (Shot Noise);242
6.7.7;7 Conclusions;245
6.7.8;Acknowledgments;246
6.7.9;References;246
6.8;Transport through Intrinsic Quantum Dots in Interacting Carbon Nanotubes;249
6.8.1;1 Introduction;249
6.8.2;2 Electrical Transport in Individual SWNTs;250
6.8.2.1;2.1 Field Theory of a Clean SWNT;250
6.8.2.2;2.2 Double Barrier Problem in a TLL;253
6.8.3;3 Markovian Master Equation Approach;256
6.8.3.1;3.1 Rate Equations;256
6.8.3.2;3.2 Conductance Peak Height;258
6.8.4;4 Quantum Monte Carlo Simulations;262
6.8.4.1;4.1 Dynamical Simulations;262
6.8.4.2;4.2 Strong Barrier Transmission;262
6.8.4.3;4.3 Weak Barrier Transmission;264
6.8.5;5 Conclusions;266
6.8.6;Acknowledgments;267
6.8.7;References;267
7;Part II Experiment;271
7.1;Contacting Individual Molecules Using Mechanically Controllable Break Junctions;273
7.1.1;1 Introduction;273
7.1.2;2 Experimental Techniques;275
7.1.2.1;2.1 Fabrication of the Electrodes;275
7.1.2.2;2.2 Deposition of Molecules;277
7.1.2.3;2.3 Measurement Techniques;279
7.1.3;3 Simple Molecules;279
7.1.4;4 Molecules Bonded by Thiol Groups to Gold;286
7.1.4.1;4.1 Low Temperatures;290
7.1.5;5 Conclusions and Prospects;291
7.1.6;Acknowledgements;291
7.1.7;References;291
7.2;Intrinsic Electronic Conduction Mechanisms in Self-Assembled Monolayers;295
7.2.1;1 Introduction;295
7.2.2;2 Experiment;297
7.2.3;3 Theoretical Basis;299
7.2.3.1;3.1 Possible Conduction Mechanisms;299
7.2.3.2;3.2 Tunneling Models;300
7.2.4;4 Results;302
7.2.4.1;4.1 Current-Voltage Characteristics;302
7.2.4.2;4.2 Inelastic Tunneling;308
7.2.5;5 Conclusions;315
7.2.6;Acknowledgements;316
7.2.7;References;316
7.3;Making Contacts to Single Molecules: Are We There Yet?;321
7.3.1;1 Introduction;321
7.3.2;2 Contact Resistance in NP Contact Experiments;323
7.3.3;3 Changing the NP Size;327
7.3.4;Acknowledgements;330
7.3.5;References;330
7.4;Six Unimolecular Recti.ers and What Lies Ahead;333
7.4.1;1 Introduction;333
7.4.2;2 Metal Contacts;338
7.4.3;3 The Aviram-Ratner Ansatz;338
7.4.4;4 Three Processes for Recti.cation by Organic Monolayers;340
7.4.5;5 Current and Resistance Across a Metal-Molecule-Metal System;341
7.4.6;6 Assembly Techniques: Physisorption Versus Chemisorption;342
7.4.7;7 The “Organic Recti.er Project”;343
7.4.8;8 Electrical Properties of Monolayers and Multilayers;345
7.4.9;9 Rectification of C16H33Q-3CNQ;345
7.4.10;10 Molecular Properties of C16H33Q-3CNQ;346
7.4.11;11 Film Properties of C16H33Q-3CNQ;347
7.4.12;12 Metal – LB Film – Metal Sandwiches of C16H33Q-3CNQ;348
7.4.13;13 Unimolecular Recti.cation by C16H33Q-3CNQ;349
7.4.14;14 Chemisorbed Monolayer Recti.ers;352
7.4.15;15 Three More Recti.ers;355
7.4.16;16 Direction of “Forward Current” in Recti.ers;358
7.4.17;17 Challenges for the Near Future;359
7.4.18;18 Conclusion;363
7.4.19;19 End-Notes;363
7.4.20;Acknowledgments;364
7.4.21;References;364
7.5;Quantum Transport in Carbon Nanotubes;371
7.5.1;1 Introduction;371
7.5.2;2 Synthesis;372
7.5.3;3 The Structure of Carbon Nanotubes;374
7.5.3.1;3.1 Lattice Structure;374
7.5.3.2;3.2 Structural Investigations of Carbon Nanotubes;374
7.5.4;4 Electronic Structure of Nanotubes;378
7.5.4.1;4.1 Energy Dispersion and Density of States of Graphene;378
7.5.4.2;4.2 Band Structure and Density of States of Carbon Nanotubes;379
7.5.5;5 Electron Transport Experiments;381
7.5.5.1;5.1 Electric Contacts;381
7.5.5.2;5.2 Ballistic Transport;383
7.5.5.3;5.3 Diffusive Transport;384
7.5.5.4;5.4 Effects of the Electron-Electron Interaction;388
7.5.6;6 Conclusions;395
7.5.7;Acknowledgements;395
7.5.8;References;395
7.6;Carbon Nanotube Electronics and Optoelectronics;401
7.6.1;1 Introduction;401
7.6.2;2 Schottky Barrier Carbon Nanotube Transistors;402
7.6.2.1;2.1 Needle-Like Contact Model;404
7.6.2.2;2.2 In.uence of the Contact Geometry;408
7.6.2.3;2.3 Effect of Gas Adsorption;410
7.6.2.4;2.4 Scaling of the SB-CNFET Performance;413
7.6.2.5;2.5 Scaling of the Drain Voltage;418
7.6.2.6;2.6 Light-Emission from a SB-CNFET;423
7.6.3;3 Conclusions and Outlook;426
7.6.4;Acknowledgements;427
7.6.5;References;427
7.7;Charge Transport in DNA-based Devices;431
7.7.1;1 Introduction;431
7.7.2;2 Direct Electrical Transport Measurements in DNA;435
7.7.2.1;2.1 Single Molecules;437
7.7.2.2;2.2 Bundles and Networks;451
7.7.2.3;2.3 Conclusions from the Experiments about DNA Conductivity;455
7.7.3;3 Conclusions and Perspectives;456
7.7.4;Acknowledgements;458
7.7.5;References;458
8;Part III Outlook;465
8.1;CMOL: Devices, Circuits, and Architectures;467
8.1.1;1 Introduction;467
8.1.2;2 Devices;469
8.1.3;3 Circuits;472
8.1.4;4 CMOL Memories;475
8.1.5;5 CMOL FPGA: Boolean Logic Circuits;480
8.1.6;6 CMOL CrossNets: Neuromorphic Networks;487
8.1.7;7 Conclusions;494
8.1.8;Acknowledgements;494
8.1.9;References;494
8.2;Architectures and Simulations for Nanoprocessor Systems Integrated on the Molecular Scale;499
8.2.1;1 Introduction;499
8.2.2;2 Starting at the Bottom: Molecular Scale Devices in Device-Driven Architectures for Nanoprocessors;502
8.2.3;3 Challenges for Nanoelectronics in Developing Nanoprocessors;505
8.2.3.1;3.1 Overview;505
8.2.3.2;3.2 Challenges Posed by the Use of Conventional Microprocessor Architectures;506
8.2.3.3;3.3 Challenges in the Development of Novel Nanoprocessing Architectures;506
8.2.4;4 A Brief Survey of Nanoprocessor System Architectures;510
8.2.4.1;4.1 Overview;510
8.2.4.2;4.2 Migration of Conventional Processor Architectures to the Molecular Scale;510
8.2.4.3;4.3 Overview of Novel Architectures for Nanoelectronics;513
8.2.5;5 Principles of Nanoprocessor Architectures Based on FPGAs and PLAs;516
8.2.5.1;5.1 Overview;516
8.2.5.2;5.2 Description of Regular Arrays, FPGAs, and PLAs: Advantages and Challenges;516
8.2.5.3;5.3 The DeHon-Wilson PLA Architecture;517
8.2.6;6 Sample Simulation of a Circuit Architecture for a Nanowire-Based Programmable Logic Array;519
8.2.6.1;6.1 Methodology for the Simulation and Analysis of Nanoprocessors;519
8.2.6.2;6.2 Device Models for System Simulation of the DeHon-Wilson NanoPLA;520
8.2.6.3;6.3 Simulations and Analyses of the NanoPLA;521
8.2.6.4;6.4 Further Implications and Issues for System Simulations;524
8.2.7;7 Conclusion;525
8.2.8;References;526
9;Index;533
10;More eBooks at www.ciando.com;0

Leseproben

CMOL: Devices, Circuits, and Architectures (p. 447-448)

Konstantin K. Likharev and Dmitri B. Strukov
Stony Brook University, Stony Brook, NY 11794, USA

Abstract. This chapter is a brief review of the recent work on various aspects of the prospective hybrid semiconductor/nanowire/molecular ("CMOL") integrated circuits. The basic idea of such circuits is to combine the advantages of the currently dominating CMOS technology (including its flexibility and high fabrication yield) with those of molecular devices with nanometer-scale footprint. Two-terminal molecular devices would be self-assembled on a pre-fabricated nanowire crossbar fabric, enabling very high function density at acceptable fabrication costs. Preliminary estimates show that the density of active devices in CMOL circuits may be as high as 1012 cm-2 and that they may provide an unparalleled information processing performance, up to 1020 operations per cm2 per second, at manageable power consumption. However, CMOL technology imposes substantial requirements (most importantly, that of high defect tolerance) on circuit architectures. In the view of these restrictions, the most straightforward application of CMOL circuits is terabitscale memories, in which powerful bad-bit-exclusion and error-correction techniques may be used to boost the defect tolerance.

The implementation of Boolean logic circuits is more problematic, though our preliminary results for reconfigurable, uniform FPGA-like CMOL circuits look very encouraging. Finally, CMOL technology seems to be uniquely suitable for the implementation of the "CrossNet" family of neuromorphic networks for advanced information processing including, at least, pattern recognition and classification, and quite possibly much more intelligent tasks. We believe that these application prospects justify a large-scale research and development effort focused on the main challenge of the field, the high-yield self-assembly of molecular devices.


1 Introduction

The recent spectacular advances in molecular electronics (for reviews see, e.g., 1–3 and other chapters of this collection), and especially the experimental demonstration of molecular single-electron transistor by several groups [4–8] give hope for the practical introduction, within the next 10 to 20 years, of the first integrated circuits with active single- or few-molecule devices. This long-expected breakthrough could not have arrived more timely. Indeed, the recent results [9,10] indicate that the current VLSI paradigm, based on a combination of lithographic patterning, CMOS circuits, and Boolean logic, can hardly be extended into a-few-nm region. The main reason is that at gate length below 10 nm, the sensitivity of parameters (most importantly, the gate voltage threshold) of silicon field-effect transistors (MOSFETs) to inevitable fabrication spreads grows exponentially. As a result, the gate length should be controlled with a few-angstrom accuracy, far beyond even the longterm projections of the semiconductor industry [11]. Even if such accuracy could be technically implemented using sophisticated patterning technologies, this would send the fabrication facilities costs (growing exponentially even now) skyrocketing, and lead to the end of Moore’s Law some time during the next decade.