Molecular-Scale Electronics

Xuefeng Guo, PhD, is a Professor at Peking University, China. His current research is focused on functional nanometer/molecular devices. Professor Guo has authored over 170 scientific publications and has received numerous scientific awards.Dong Xiang, PhD, is a Professor in the College of Electronic Information and Optical Engineering, Nankai University. His current research interests focus on single molecule studies and optoelectronic molecular devices.Yu Li, PhD, is a research scientist in the College of Chemistry and Molecular Engineering at Peking University, China. Her research interest includes single-molecule device physics and biophysics.

• 1 Introduction 12 Metal Electrodes for Molecular Electronics 72.1 Single-Molecule Junctions 72.1.1 Scanning Probe Microscopy Break Junctions 72.1.1.1 Beyond Traditional SPM Break Junctions 132.1.1.2 Applications of SPM Beyond Electron Transport 162.1.2 Mechanically Controllable Break Junctions 192.1.2.1 Work Principle and Advantages 192.1.2.2 MCBJ Chip Fabrication 232.1.2.3 MCBJ Applications 252.1.3 Electromigration Breakdown Junctions 322.1.3.1 Device Fabrication 332.1.3.2 Gap Size Control 342.1.3.3 Electromigration Applications 372.1.4 Electrochemical Deposition Junctions 402.1.5 Surface-Diffusion-Mediated Deposition Junctions 432.2 Ensemble Molecular Junctions 452.2.1 Lift-and-Float Approach 452.2.2 Liquid Metal Contact 472.2.3 Nanopore and Nanowell 502.2.4 On-Wire Lithography 522.2.5 Transfer Printing Techniques 542.2.6 Self-Aligned Lithography 602.2.7 Buffer Interlayer-Based Junction 622.2.8 On-Edge Molecular Junction 652.2.9 Suspended-Wire Molecular Junctions 683 Carbon Electrodes for Molecular Electronics 933.1 Carbon Nanotube-Based Electrodes 933.1.1 Electrical Breakdown 943.1.2 Lithography-Defined Oxidative Cutting 983.2 Graphene-Based Electrodes 1023.2.1 Electroburning 1033.2.2 Dash-Line Lithography 1033.3 Other Carbon-Based Electrodes 1074 Other Electrodes for Molecular Electronics 1134.1 Silicon-Based Electrodes 1134.2 Polymer-Based Electrodes 1165 Novel Phenomena in Single-Molecule Junctions 1195.1 Quantum Interference 1195.1.1 Prediction of QI Effects 1195.1.2 Signature of Quantum Interference 1205.1.3 Different Transport Pathways 1235.1.4 Chemical Design to Tune Quantum Interference 1245.2 Coulomb Blockade and Kondo Resonance 1255.3 Thermoelectricity 1285.4 Electronic–Plasmonic Conversion 1306 Supramolecular Interactions in Single-Molecule Junctions 1376.1 Hydrogen Bonds 1376.2 π–π Stacking Interactions 1406.3 Host–Guest Interactions 1446.4 Charge-Transfer Interactions 1497 Characterization Techniques for Molecular Electronics 1577.1 Inelastic Electron Tunneling Spectroscopy 1577.1.1 History and Background 1587.1.2 IETS Measurement 1607.1.3 IETS Applications 1637.2 Temperature–Length–Variable Transport Measurement 1667.3 Noise Spectroscopy 1707.3.1 Thermal Noise and Shot Noise 1717.3.2 Generation–Recombination and Flicker Noise 1727.3.3 Noise Spectroscopy Measurements 1737.3.4 Application of Noise Spectroscopy 1747.4 Optical and Optoelectronic Spectroscopy 1807.4.1 Raman Spectroscopy 1807.4.2 Ultraviolet–Visible Spectroscopy 1827.4.3 X-ray Photoelectron Spectroscopy 1837.4.4 Ultraviolet Photoelectron Spectroscopy 1847.5 Data Characterization Approaches 1857.5.1 Transition Voltage Spectroscopy 1857.5.1.1 TVS Models 1857.5.1.2 Applications of TVS 1887.5.2 One Dimensional (1D), Two Dimensional (2D) Histogram and QuB 1918 Theoretical Aspects for Electron Transport Through Molecular Junctions 2098.1 Theoretical Description of the Tunneling Process 2098.2 Electron Transport Mechanism 2128.2.1 Coherent Electron Transport Through Molecular Junctions 2128.2.2 Electron–Phonon Interaction Effects on Transport Mechanism 2148.3 First-Principles Modeling 2158.3.1 Introduction to Density Functional Theory 2158.3.2 Current–Voltage Characteristics Calculations 2179 Integrating Molecular Functionalities into Electrical Circuits 2259.1 Wiring Toward Nanocircuits 2259.1.1 Backbones as Charge Transport Pathways 2269.1.1.1 Hydrocarbon Chains 2279.1.1.2 Metal Containing Compounds 2349.1.1.3 Porphyrin Arrays 2379.1.1.4 Carbon Nanotubes 2399.1.1.5 Biological Wires 2419.1.2 Conductance of Single Molecules 2449.1.2.1 Interfacial Coupling 2459.1.2.2 Energy Level Alignment 2509.1.2.3 Photon-Assisted Conductance Enhancement 2529.1.2.4 Molecular Conductance Measurements 2569.2 Rectification Toward Diodes 2589.2.1 General Mechanisms for Molecular Rectification 2599.2.1.1 Aviram–Ratner Model 2599.2.1.2 Kornilovitch–Bratkovsky–Williams Model 2619.2.1.3 Datta–Paulsson Model 2629.2.2 Rectification Stemming from Molecules 2629.2.2.1 D–σ–A and D–π–A System 2629.2.2.2 D–A Diblock Molecular System 2639.2.3 Rectification Stemming from Different Interfacial Coupling 2679.2.3.1 Different Electrodes 2679.2.3.2 Anchoring Groups 2689.2.3.3 Contact Geometry 2699.2.3.4 Interfacial Distance 2699.2.4 Other Molecular Rectifiers 2709.3 Negative Differential Conductance Toward Oscillators 2729.3.1 Mechanisms for Negative Differential Conductance 2729.3.2 Measurement of NDC 2749.3.3 Application of NDC 2769.4 Gating Toward Molecular Transistors 2779.4.1 Back Gating for Novel Physical Phenomenon Investigation 2779.4.2 Side Gating for Electron Transport Control 2829.4.3 Electrochemical Gating for Efficient Gate Coupling 2839.5 Switching Toward Memory Devices 2849.5.1 Switch Stem from Conformation Change 2859.5.1.1 Electrical Field Induced Switch 2859.5.1.2 Tunneling Electron (Charge) Triggered Switch 2869.5.1.3 Mechanical Force Induced Switch 2899.5.1.4 Chemical Stimuli Triggered Switch (Redox and pH) 2909.5.1.5 Light-Triggered Switch 2939.5.2 Electrochemically Gated Switch 2979.5.3 Spintronics-Based Switch 3019.5.4 Other Memory Devices 3059.6 Molecular Computing 3069.6.1 DNA-Based Computing 3069.6.2 Molecular Logic Gates 3089.7 Transduction Toward Molecular Sensors 3139.7.1 Sensing Based on Chemical Reactions 3149.7.2 Sensing Based on Biological Interactions 3199.7.2.1 Nanocarbon-Based Molecular Electronics 3219.7.2.2 Silicon-Based Devices 3279.7.3 Sensing Based on Thermoelectrical Conversion 3319.8 High-Frequency Molecular Devices 3339.9 Molecular Machines 3379.9.1 Molecular Motors 3379.9.2 Molecular Elevators 3389.9.3 Molecular Scissors 3419.9.4 Other Multicomponent Mechanical Machines 34410 Summary and Perspectives 37510.1 Primary Challenges 37710.1.1 In Situ Measurement 37710.1.2 Device Fabrication Yield 37810.1.3 Device-to-Device Variation and Instability 37810.1.4 Integration Capability 37910.1.5 Energy Consumption 38010.1.6 Addressability 38010.1.7 General Strategies to Meet Challenges 38110.2 Open Questions 38210.3 Outlook 384References 385Index 389