Electrical and Optoelectronic Properties of the Nanodevices Composed of Two-Dimensional Materials (eBook)

Cheng-Hua Liu graduated from National Taiwan University with a major in Physics. He obtained his Ph.D. in May 2016. His research projects involve investigations on the graphene p-n-p junction and the MoS2 thin-film transistor using the resistor-free fabrication method. His main project is based in Prof. Chi-Te Liang’s lab at National Taiwan University and Wei-Hua Wang’s lab at the Institute of Atomic and Molecular Sciences.

Supervisor’s Foreword 6
Abstract 8
Acknowledgements 10
Contents 11
1 Introduction 14
References 15
2 Theoretical Background 16
2.1 Physical Properties of Graphene 16
2.1.1 Electrical Structure and Zero Band Gap 16
2.1.2 Pseudospin 18
2.1.3 Klein Tunneling 19
2.1.4 Quantum Hall Effect 21
2.1.5 Shubnikov-de Haas Oscillation and Massless Effective Mass 24
2.1.6 Quantum Hall Plateau-Plateau Transition 26
2.1.7 Weak Localization 26
2.2 Molybdenum Disulfide (MoS2) 29
2.2.1 Photoconductivity Effect 29
2.2.2 Persistent Photoconductivity 30
References 33
3 Experimental Methods 35
3.1 Resist-Free Fabrication 35
3.2 Physical Property Measurement System 36
3.3 Optical Measurement Systems 37
3.4 Atomic Force Microscopy 39
3.5 OTS-Functionalized Substrates and Electrical Measurement Method 40
3.5.1 OTS-Functionalized Substrates 40
3.5.2 Two-Terminal Conductance Measurements 41
References 42
4 Distinctive Magnetotransport of Graphene p-n-p Junctions via Resist-Free Fabrication and Controlled Diffusion of Metallic Contact 44
4.1 Introduction 44
4.2 Fabrication 45
4.3 Experimental Results 45
4.4 Demonstration of p-n Junction Devices 49
4.5 Conclusion 50
References 51
5 Observation of Quantum Hall Plateau-Plateau Transition and Scaling Behavior of the Zeroth Landau Level in Graphene p-n-p Junction 52
5.1 Introduction 52
5.2 Fabrication 53
5.3 Experimental Results 53
5.3.1 The Doping Effect from Titanium Diffusion 53
5.3.2 The Doping Effect Simulated by Theoretical Dipining Model 55
5.3.3 Characteristics of Graphene p-n-p Junction Devices 56
5.3.4 Quantum Hall Effect in p-n-p Junction 58
5.3.5 Scaling Behavior 60
5.3.6 The MR and the Distribution of the Energy Levels of the LLs 61
5.4 Conclusion 63
References 63
6 Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect 65
6.1 Introduction 65
6.2 Fabrication 66
6.3 Measurement Method 67
6.4 Experimental Results and Discussion 68
6.4.1 The PPC Effect in a Monolayer MoS2 Transistor 68
6.4.2 Temperature Dependence of PPC Relaxation 70
6.4.3 The Subtract Effect of PPC 71
6.4.4 Discussion of PPC Mechanism 73
6.4.5 The Relationship Between the PPC Effect and Transport Behavior 75
6.4.6 Fitting of the PPC Relaxation Curves 75
6.4.7 Gate Voltage Dependence of the PPC 76
6.4.8 Transport Characteristics of the MoS2 FET 77
6.4.9 Carrier Mobility Dependence of the PPC 78
6.5 Conclusion 79
References 79
7 Conclusion 82