Handbook of Single-Molecule Electronics

Single-molecule electronics has evolved as a vibrant research field during the last two decades. The vision is to be able to create electronic components at the highest level of miniaturization-the single molecule. This book compiles and details cutting-edge research with contributions from chemists, physicists, theoreticians, and engineers. It covers all aspects of single-molecule electronics, from the theory through experimental realizations and the chemical synthesis of molecular components to the implementation of molecular components in future integrated circuits. This book describes in detail both established methods and recent advances in the field, including vibrational effects, switching phenomena, quantum interference, thermal power, and parallel assembly strategies. Read more... Abstract: Single-molecule electronics has evolved as a vibrant research field during the last two decades. The vision is to be able to create electronic components at the highest level of miniaturization-the single molecule. This book compiles and details cutting-edge research with contributions from chemists, physicists, theoreticians, and engineers. It covers all aspects of single-molecule electronics, from the theory through experimental realizations and the chemical synthesis of molecular components to the implementation of molecular components in future integrated circuits. This book describes in detail both established methods and recent advances in the field, including vibrational effects, switching phenomena, quantum interference, thermal power, and parallel assembly strategies Handbook of Single-Molecule Electronics 3 Contents 5 Preface 13 Chapter 1 - Introduction 15 Chapter 2 - Experimental Techniques 19 2.1 Introduction 19 2.2 Experimental Techniques 20 2.2.1 Mechanical Techniques 21 2.2.1.1 Scanning tunneling microscope 22 2.2.1.2 Atomic force microscope 23 2.2.1.3 Mechanically controlled break junction 25 2.2.2 Nanofabrication Methods 27 2.2.2.1 Electromigration 27 2.2.2.2 Evaporation methods 28 2.2.2.3 Direct manipulation methods 29 2.2.2.4 Low-dimensional electrode materials 30 2.2.3 Self-Assembled Devices 32 2.3 Identifying Single Molecules in Devices 33 2.3.1 Statistics 33 2.3.2 Single-Molecule Signatures 34 2.3.3 Possible Artifacts 37 2.4 Summary and Conclusion 38 Problems 38 References 39 Chapter 3 - Basic Theory of Electron Transport Through Molecular Contacts 45 3.1 Introduction 45 3.2 Electron Transport Through a Single-Level Quantum Dot 48 3.3 Recursive Green’s Function Technique 57 3.3.1 Local Properties 61 3.3.2 Further Optimizations 63 3.4 Graphene Leads: Gate-Tunable Quantum Coherent Transport 64 3.5 Molecular Contact between Superconducting Leads 75 3.5.1 General Methods 77 3.5.2 One-Iteration Approximation 80 3.5.3 Results 81 3.6 Summary 86 Acknowledgments 86 Problems 87 References 88 Chapter 4 - First-Principles Simulations of Electron Transport in Atomic-Scale Systems 93 4.1 Introduction 93 4.2 The DFT+NEGF Approach 95 4.3 Application: Conductance of a Single C60 Molecule Junction—Atom-by-Atom Engineering of the Electrode Interface 99 4.4 Electron-Vibration Interactions 106 4.5 Inelastic Transport with DFT+NEGF 109 4.6 Lowest-Order Expansion Approach 112 4.7 Application: Inelastic Conductance Signals in Atomic Gold Chains 115 4.8 Inelastic Effects in Shot Noise 119 4.9 Application: Inelastic Shot Noise Signals in a Gold Point Contact 121 4.10 Summary 124 Problems 124 References 125 Chapter 5 - Controlling the Molecule–Electrode Contact in Single-Molecule Devices 130 5.1 Introduction and Background 131 5.2 Contact Resistance of Molecular Wires 134 5.3 Molecular Linkers and Contact Geometry 140 5.3.1 Break-Junction Techniques for Single-Molecule Junctions 141 5.3.2 Alkanedithiols 143 5.3.3 Varying the Molecule–Electrode Contact 148 5.4 Mechanical Control of Molecule–Electrode Coupling 151 5.5 Mechanical Control of Molecular Energy Levels 155 5.6 Summary and Conclusions 158 Acknowledgments 158 Problems 159 References 159 Chapter 6 - Vibrational Excitations in Single-Molecule Junctions 168 6.1 Introduction 169 6.2 Vibrational Modes 170 6.2.1 Born–Oppenheimer Approximation 171 6.2.2 Harmonic Oscillator 172 6.2.3 Morse Potential 174 6.3 Franck–Condon Principle 175 6.3.1 Electron–Phonon Coupling 177 6.3.2 Recursion Relations 178 6.3.2.1 Single harmonic oscillator 178 6.3.2.2 Multiple harmonic oscillators 180 6.3.3 Numerical Evaluation 183 6.3.3.1 Example: emission spectrum of Pt(4,6-dFppy)(acac) 183 6.4 Vibrational Modes in Transport:Weak-Coupling Regime 185 6.4.1 Master Equation 185 6.4.1.1 Transition rates 186 6.4.1.2 Calculating the properties of interest 188 6.4.1.3 Numerical evaluation 189 6.4.2 Selection Rules 191 6.4.2.1 Single-level model 191 6.4.2.2 Example: weakly coupled OPV-5 junction 193 6.5 Vibrational Modes in Transport: Strong-Coupling Regime 196 6.5.1 Nonequilibrium Green’s Function Formalism 197 6.5.1.1 Second quantization 197 6.5.1.2 Elastic transport 198 6.5.1.3 Inelastic transport 200 6.5.2 Selection Rules 203 6.5.2.1 Example: strongly coupled OPE-3 junction 203 6.5.3 Franck–Condon Factors Revisited 206 Problems 210 References 211 Chapter 7 - Self-Assembly at Interfaces 218 7.1 Introduction 219 7.2 Self-Assembled Monolayers 222 7.2.1 Inter- and Intramolecular Interactions between the Molecule and the Surface 222 7.2.2 Chemisorption vs Physisorption 227 7.2.3 How Do Molecules Arrange on a Gold Surface? 230 7.2.4 Adsorption Sites on Gold [Au(111)] 232 7.3 Gold and Other Materials 236 7.3.1 Why is Gold the Most Prominent Example for Self-Assembly? 236 7.3.2 Silicon Surfaces 238 7.3.3 Graphene for Self-Assembled Electrodes 239 7.4 Summary and Conclusion 241 Problems 241 References 242 Chapter 8 - Molecular Switches 246 8.1 Introduction 246 8.2 Redox-Controlled Switches 247 8.2.1 Redox-Active Molecules 248 8.2.2 Hydroquinone–Quinone and OPV Switches 249 8.2.3 Tetrathiafulvalene and Molecular Cruciforms 249 8.2.4 Spin-Crossover Metal Complexes 253 8.2.5 Bipyridyl-OPE Switch 254 8.2.6 Mechanically Interlocked Molecules 255 8.3 Light-Controlled Switches 258 8.3.1 Diazobenzene 259 8.3.2 Dithienylethenes 260 8.3.3 Dihydroazulene 262 8.4 Coordination-Induced Switches 266 8.5 Tautomerization-Induced Switches 267 8.6 Concluding Remarks 268 Problems 269 References 270 Chapter 9 - Switching Mechanisms in Molecular Switches 275 9.1 Introduction 276 9.2 Switching Behavior: Stochastic or Deterministic? 277 9.3 Bianthrone Switch 279 9.3.1 Experimental Data 279 9.3.2 General Model for Switching 280 9.3.3 Data Analysis 284 9.4 C60 Junction 287 9.4.1 Experimental Data 287 9.4.2 Switching Rates: Forward Switching 289 9.4.3 Switching Rates: Reverse Switching 291 9.4.4 Potential Landscape and On-Off Hysteresis 292 9.4.5 What are the On and Off states? 294 9.4.6 Switching by Tunneling: Approaching the Classical Limit 296 9.5 Switching Behavior of OPV3 Junction 297 9.5.1 Experimental Data 297 9.5.2 Data Analysis 298 9.5.3 The On and Off States of the OPV3 Junction 302 9.6 Summary 303 Problems 304 References 308 Chapter 10 - Thermoelectricity in Molecular Junctions 311 10.1 Introduction 311 10.2 Electronic Conductance 316 10.3 Thermal Conductance 317 10.4 Molecular Junctions 319 10.4.1 Thermoelectricity 321 10.5 Transmission Functions and ZT 323 10.5.1 Electronic Transmission Functions 323 10.5.2 Phonon Transmission Functions 326 10.5.3 Computational Studies of Thermal Transport in Molecular Junctions 328 10.5.4 ZT and Thermoelectric Efficiency 329 10.6 Experimental Techniques for Probing Transport Properties of Molecular Junctions 331 10.6.1 Formation of Metal–Molecule–Metal Junction 331 10.6.2 Scanning Tunneling Microscope Break Junction (STM-BJ) Technique 332 10.6.3 Contact Probe Atomic Force Microscope Technique 340 10.7 Experimental Techniques for Probing the Heat Dissipation and Heat Transport Properties of Single-Molecule Junctions 342 10.8 Summary 343 Problems 346 References 347 Chapter 11 - Interference Effects in Single-Molecule Transport 352 11.1 Introduction 352 11.2 Why Interference? 354 11.3 Interest in Interference Effects 357 11.4 Signatures of Interference 359 11.4.1 In a Model-System Calculation 359 11.4.2 In a More Realistic Calculation 359 11.4.3 In Experimental Measurements 362 11.5 Range of Chemical Systems 366 11.5.1 Predicting Interference Effects 366 11.6 What is Interfering with What? 370 11.7 (How) CanWe Use Interference Effects? 372 11.7.1 Switching 372 11.7.2 Chemical Control 374 11.8 Conclusion 375 Problems 376 References 377 Chapter 12 - Parallel Self-Assembly Strategies toward Multiple Single-Molecule Electronic Devices 381 12.1 Introduction 382 12.1.1 Self-Assembly of Nanomaterials 383 12.2 Self-Assembly on Surfaces 384 12.2.1 Self-Assembly at the Air–Water Interface 387 12.3 Solution Assembly of Molecular Nanogaps 390 12.4 Conclusion 399 Problems 400 References 400 Chapter 13 - Toward Circuit Design in Single-Molecule Electronics 406 13.1 Tunneling, Coulomb Blockade, and Addition Energy 407 13.2 Island Excited by an Ideal Current Source and Zero Tunneling Time 411 13.3 Island Excited by an Ideal Voltage Source and Zero Tunneling Time 413 13.4 Single-Electron Tunneling Transistor 416 13.5 Including Nonzero Tunneling Times 421 13.6 Circuit Perspectives 425 13.7 Summary 426 Appendix A - Delta Pulse Description 427 Appendix B - Tunneling and the Delta Pulse Description 428 Problems 429 References 429 Index 431 1. Introduction / Kasper Moth-poulsen -- 2. Experimental Techniques / Kasper Moth-poulsen -- 3. Basic Theory Of Electron Transport Through Molecular Contacts / Anders Bergvall, Mikael Fogelstrom, Cecilia Holmqvist, And Tomas Lofwander -- 4. First-principles Simulations Of Electron Transport In Atomic-scale Systems / Thomas Frederiksen -- 5. Controlling The Molecular-electrode Contact In Single-molecule Devices / Joshua Hihath -- 6. Vibrational Excitations In Single-molecule Junctions / Johannes S. Seldenthuis, Herre S.j. Van Der Zant, And Joseph M. Thijssen -- 7. Self-assembly At Interfaces / Tina A. Gschneidtner And Kasper Moth-poulsen -- 8. Molecular Switches / Mogens Brndsted Nielsen -- 9. Switching Mechanisms In Molecular Switches / Andrey Danilov And Sergey Kubatkin -- 10. Thermoelectricity In Molecular Junctions / Shubhaditya Majumdar, Won Ho Jeong, Pramod S. Reddy, And Jonathan A. Malen -- 11. Interference Effects In Single-molecule Transport / Gemma C. Solomon -- 12. Parallel Self-assembly Strategies Toward Multiple Single-molecule Electronic Devices / Kasper Nrgaard And Titoo Jain -- 13. Toward Circuit Design In Single-molecule Electronics / Jaap Hoekstra. Edited By Kasper Moth-poulsen Includes Bibliographical References And Index. Content: Introduction / Kasper Moth-Poulsen -- Experimental techniques / Kasper Moth-Poulsen -- Basic theory of electron transport through molecular contacts / Anders Bergvall, Mikael Fogelström, Cecilia Holmqvist, and Tomas Löfwander -- First-principles simulations of electron transport in atomic-scale systems / Thomas Frederiksen -- Controlling the molecular-electrode contact in single-molecule devices / Joshua Hihath -- Vibrational excitations in single-molecule junctions / Johannes S. Seldenthuis, Herre S.J. van der Zant, and Joseph M. Thijssen -- Self-assembly at interfaces / Tina A. Gschneidtner and Kasper Moth-Poulsen -- Molecular switches / Mogens Brøndsted Nielsen -- Switching mechanisms in molecular switches / Andrey Danilov and Sergey Kubatkin -- Thermoelectricity in molecular junctions / Shubhaditya Majumdar, Won Ho Jeong, Pramod S. Reddy, and Jonathan A. Malen -- Interference effects in single-molecule transport / Gemma C. Solomon -- Parallel self-assembly strategies toward multiple single-molecule electronic devices / Kasper Nørgaard and Titoo Jain -- Toward circuit design in single-molecule electronics / Jaap Hoekstra. Single-molecule electronics has evolved as a vibrant research field during the last two decades. The vision is to be able to create electronic components at the highest level of miniaturization―the single molecule. This book compiles and details cutting-edge research with contributions from chemists, physicists, theoreticians, and engineers. It covers all aspects of single-molecule electronics, from the theory through experimental realizations and the chemical synthesis of molecular components to the implementation of molecular components in future integrated circuits. This book describes in detail both established methods and recent advances in the field, including vibrational effects, switching phenomena, quantum interference, thermal power, and parallel assembly strategies. The authors add more details to the chapters than typically found in the primary literature so that the book can be read not only by specialists but also by non-experts and students with an interest in the research field. Each chapter is accompanied by problems, and a solutions manual is also provided.