Unique in its scope, this book comprehensively combines various synthesis strategies with applications for nanogap electrodes. Clearly divided into four parts, the monograph begins with an introduction to molecular electronics and electron transport in molecular junctions, before moving on to a whole section devoted to synthesis and characterization. The third part looks at applications with single molecules or self-assembled monolayers, and the whole is rounded off with a section on interesting phenomena observed using molecular-based devices.

Table of Contents:
Preface xi 1 Nanogap Electrodes and Molecular Electronic Devices 1 Tao Li 1.1 Introduction 1 1.2 Overview of Molecular Electronics 2 1.2.1 Why Molecular Electronics 3 1.2.1.1 History of Computing 3 1.2.1.2 Moore’s Law 6 1.2.1.3 Molecular Electronics: A Beyond-CMOS Option 8 1.2.2 Molecular Materials for Organic Electronics 10 1.2.2.1 OLEDs 11 1.2.2.2 OFETs 11 1.2.2.3 OPVs 12 1.2.3 Molecules for Molecular-Scale Electronics 13 1.3 Introduction to Nanogap Electrodes 16 1.4 Summary and Outlook 19 References 19 2 Electron Transport in Single Molecular Devices 25 Lei-Lei Nian, Liang Ma, and Jing-Tao Lü 2.1 Introduction 25 2.2 General Methods 26 2.2.1 Transport Mechanisms 26 2.2.2 Nonequilibrium Green’s Function Method 26 2.2.3 Master Equation Method 29 2.3 Single Electron Transport Through Single Molecular Junction 31 2.3.1 Coherent Transport 31 2.3.2 Hopping Transport 32 2.4 Effect of Many-Body Interactions 35 2.4.1 Electron-Vibration Interaction 35 2.4.1.1 Weak Coupling Regime 37 2.4.1.2 Strong-Coupling Regime 40 2.4.2 Electron–Electron Interaction 43 2.4.2.1 Coulomb Blockade 43 2.4.2.2 Kondo Effect 45 2.5 Thermoelectric Transport 48 2.6 First-Principles Simulations of Transport in Molecular Devices 51 2.7 Conclusions 52 References 52 3 Fabricating Methods and Materials for Nanogap Electrodes 57 Xianhui Huang, Weiqiang Zhang, Dong Xiang, and Tao Li 3.1 Introduction 57 3.2 Mechanical Controllable Break Junctions 59 3.3 Electrochemical and Chemical Deposition Method 68 3.3.1 Electroplating and Feedback System 68 3.3.2 Chemical Deposition 74 3.4 Oblique Angle Shadow Evaporation 75 3.5 Electromigration and Electrical Breakdown Method 78 3.5.1 Device Fabrication 79 3.5.2 Gap Size Control 82 3.5.3 Electromigration Applications 84 3.6 Molecular Scale Template 89 3.6.1 Molecular Rulers 89 3.6.2 Inorganic Films as Templates 94 3.6.3 On-Wire Lithography 96 3.6.4 Nanowire Mask 100 3.7 Focused Ion Beam 102 3.8 Scanning Probe Lithography and Conducting Probe-Atomic Force Microscopy 108 3.8.1 DestructiveWay 108 3.8.2 ConstructiveWay 111 3.8.3 Conducting Probe-Atomic Force Microscopy 112 3.9 Nanogap Electrodes Prepared with Nonmetallic Materials 113 3.9.1 Introduction 113 3.9.2 Nanogap Electrodes Made from Carbon Materials 114 3.9.2.1 Advantages of Carbon Materials 114 3.9.2.2 Carbon Nanotubes for Nanogap Electrodes 115 3.9.2.3 Graphene 130 3.9.2.4 Silicon Nanogap Electrodes 153 3.9.2.5 Other Materials 171 3.10 Summary and Outlook 174 References 175 4 Characterization Methods and Analytical Techniques for Nanogap Junction 189 Baili Li, Ziyan Wang, Bin Han, and Xi Yu 4.1 Current–Voltage Analysis 189 4.1.1 Coherent Tunneling Transport 190 4.1.2 Transition Voltage Spectroscopy 195 4.1.3 Incoherent Transport 198 4.2 Inelastic Tunneling Spectroscopy (IETS) 206 4.2.1 Principle and Measurement of IETS 206 4.2.2 Selection Rule and Charge Transport Pathway 209 4.2.3 Line Shape of the IETS 214 4.2.4 Application of the IETS 218 4.2.5 Mapping the Charge Transport Pathway in Protein Junction by IETS 219 4.2.6 STM Imaging by IETS 222 4.3 Optical and Optoelectronic Spectroscopy 226 4.4 Concluding Remarks 232 Appendix 233 References 234 5 Single-Molecule Electronic Devices 239 Shengxiong Xiao 5.1 Introduction 239 5.2 Wiring Molecules into “Gaps”: Anchoring Groups and Assembly Methods 240 5.2.1 Anchor Groups 240 5.2.2 Effect of Anchor–Bridge Orbital Overlaps on Conductance 245 5.2.3 In Situ Chemical Reactions to Produce Covalent Contacts 250 5.3 Electrical Rectifier 252 5.3.1 Rectification Toward Diodes 255 5.3.2 General Mechanisms for Molecular Rectification 256 5.3.2.1 Aviram–Ratner Model 256 5.3.2.2 Kornilovitch–Bratkovsky–Williams Model 257 5.3.2.3 Datta–Paulsson Model 258 5.3.3 Rectification Originated from Molecules 259 5.3.3.1 D–σ–A and D–π–A Systems 259 5.3.3.2 D–A Diblock Molecular System 260 5.3.4 Rectification Stemming from Different Interfacial Coupling 264 5.3.4.1 Different Electrodes 264 5.3.4.2 Anchoring Groups 265 5.3.4.3 Contact Geometry 265 5.3.4.4 Interfacial Distance 266 5.3.5 Additional Molecular Rectifiers 267 5.4 Conductance Switches 269 5.4.1 Voltage Pulse Induced Switches 270 5.4.2 Light-Induced Switching 271 5.4.3 Switching Triggered by Chemical Process (Redox and pH) 275 5.4.4 Spintronics-Based Switch 278 5.5 Gating the Transport: Transistor-Like Single-Molecule Devices 282 5.5.1 Electrostatic Gate Control 282 5.5.2 Side Gating 287 5.5.3 Electrochemical Gate Control 288 5.5.4 Molecular Quantum Dots 290 5.6 Challenges and Outlooks 291 References 292 6 Molecular Electronic Junctions Based on Self-Assembled Monolayers 301 Yuqing Liu and Zhongming Wei 6.1 Introduction 301 6.2 Molecular Monolayers for Molecular Electronics Devices 302 6.2.1 Monolayers Covalently Bonded to Noble Metals 303 6.2.2 Monolayers Attached to Non-metal Substrates 309 6.2.3 Langmuir–Blodgett Method 312 6.3 Top Electrodes 314 6.3.1 Deposited Metal 314 6.3.1.1 Direct Evaporation 315 6.3.1.2 Indirect Evaporation 316 6.3.2 Make Top Contact by Soft Methods 319 6.3.2.1 Lift-and-Float Approach 319 6.3.2.2 Crosswire Junction 320 6.3.2.3 Transfer Printing 322 6.3.2.4 Graphene as Top Electrode 323 6.3.2.5 Liquid Metal Contact 326 6.4 Experimental Progress with Ensemble Molecular Junctions 329 6.5 Outlook 334 References 335 7 Toward Devices and Applications 345 Ajuan Cui and Kasper Nørgaard 7.1 Introduction 345 7.2 Major Issues: Reliability and Robustness 346 7.2.1 Single Molecular Device 347 7.2.1.1 Top-Contact Junctions 347 7.2.1.2 Planar Metallic Nanogap Electrodes 347 7.2.1.3 Planar Nanogap Electrodes Based on SingleWalled Carbon Nanotubes (SWCNTs) or Graphene 349 7.2.1.4 The Absorption of Molecule on the Surface of SWCNTs or Graphene 350 7.2.2 Molecular Device Based on Molecule Monolayer 351 7.2.2.1 Bottom Electrodes 353 7.2.2.2 Insulating Layer with Holes to Define the Size of the Bottom Electrodes 353 7.2.2.3 Molecule Monolayer Formation 354 7.2.2.4 Top Electrodes 354 7.3 Potential Integration Solutions 358 7.3.1 Carbon Nanotube or Graphene Interconnects 359 7.3.2 Self-Assembled Monolayers for Integrated Molecular Junctions 364 7.3.3 Cross Bar Architecture 368 7.4 Beyond Simple Charge Transport 371 7.4.1 Mechanics 371 7.4.2 Thermoelectronics 375 7.4.3 Quantum Interference 381 7.4.4 Spintronics 386 7.4.4.1 SAM-Based Magnetic Tunnel Junctions 386 7.4.4.2 Molecule Based Spin-Valves or Magnetic Tunnel Junctions 387 7.4.4.3 Single Molecular Spin Transistor 389 7.4.4.4 Single Molecular Nuclear Spin Transistor 391 7.4.4.5 Molecule Based Hybrid Spintronic Devices 393 7.5 Electrochemistry with Nanogap Electrodes 395 References 400 Index 411