Properties of Synthetic Two-Dimensional Materials and Heterostructures (eBook)

Yu-Chuan Lin received his PhD from Pennsylvania State University in 2017. He now has a postdoctoral research position at Oak Ridge National Laboratory. 

Supervisor’s Foreword 6
Preface 8
Acknowledgments 10
Contents 12
Chapter 1: Two-Dimensional Materials 16
1.1 Introduction 16
1.2 Classification and Thermal Stability 18
1.3 Graphene: The Beginning of 2D Materials Research 21
1.4 Monolayer Transition Metal Dichalcogenides: Real 2D Semiconductors 22
1.5 2D Materials as the Building Blocks for vdW Heterostructures 26
1.5.1 Making vdW Heterostructures via Stacking Exfoliated 2D Layers 27
1.5.2 Applications of vdW Heterostructures for Electrical and Optical Devices 28
1.5.3 Interfacial Imperfection 30
References 32
Chapter 2: Synthesis and Properties of 2D Semiconductors 35
2.1 Introduction 35
2.2 Molecular Absorption and Desorption Process During Thin-Film Deposition 36
2.2.1 Nucleation and Growth 37
2.2.2 Epitaxial Relationship Between Deposited Materials and Substrates 39
2.3 Synthesis Techniques for 2D TMDC 40
2.3.1 Powder Vaporization 41
2.3.2 Metal-Organic Chemical Vapor Deposition 43
2.3.3 Epitaxial Graphene Synthesis 43
2.4 Vertical and Radical Heterostructures Based on Synthetic 2D Materials 44
2.5 2D Materials Electronics: Interface Is Critical 49
2.6 2D Semiconductors for Low-Power Electronic Applications 52
2.6.1 Scalable Process for Synthetic 2D Semiconductors 53
References 56
Chapter 3: Properties of Atomically Thin WSe2 Grown Via Metal-Organic Chemical Vapor Deposition 58
3.1 Impact of Growth Conditions and Substrates on Properties of WSe2 58
3.1.1 Introduction 58
3.1.2 Experimental Methods 59
Material Synthesis 59
Materials Characterization 60
Device Fabrication and Tunneling Current Measurements 60
3.1.3 Results and Discussion 61
3.1.4 Conclusions for Sect. 3.1 66
3.2 Toward Large-Area and Epitaxy-Grade WSe2 67
3.2.1 Introduction 67
3.2.2 Experimental Methods 68
Materials Characterization 68
Impurity of Precursor and Growth Steps of Epitaxial WSe2 69
Electrolyte-Gating Electrical Measurement 70
3.2.3 Results and Discussion 72
Epitaxial Growth of WSe2 72
Kinetics for WSe2 Growth 75
Domain Boundaries of Epitaxial WSe2 76
WSe2–Sapphire Interface 77
Electronic Transport of Epitaxial WSe2 80
3.3 Conclusions 83
References 83
Chapter 4: Direct Synthesis of van der Waals Solids 86
4.1 Introduction 86
4.2 Experimental Methods 88
4.2.1 Materials Synthesis 88
4.2.2 Fabrication and Measurement of MoS2 Photosensors 88
4.2.3 Materials Characterization 89
4.3 Results and Discussion 89
4.4 Conclusions 98
References 99
Chapter 5: Atomically Thin Heterostructures Based on Monolayer WSe2 and Graphene 101
5.1 Introduction 101
5.2 Experimental Methods 102
5.2.1 Growth and Properties of WSe2 Layers on Graphene 102
5.2.2 Diode Fabrication 103
5.2.3 LEEM for Assessment of the Graphene Layer Thickness 104
5.3 Results and Discussion 104
5.4 Conclusions 112
References 112
Chapter 6: Tuning Electronic Transport in WSe2-Graphene 114
6.1 Introduction 114
6.2 Experimental Methods 115
6.3 Results and Discussion 117
6.3.1 WSe2 Synthesis and Buffer-Layer Decoupling 117
6.3.2 LEEM/LEER Measurements and Analysis 118
6.3.3 Conductive AFM I–V Characteristics and Band Alignment Model 119
6.4 Conclusions 122
References 122
Chapter 7: Atomically Thin Resonant Tunnel Diodes 124
7.1 Introduction 124
7.2 Experimental Methods 125
7.2.1 Epitaxial Graphene Grown on 6H-SiC 125
7.2.2 MoS2-WSe2-EG and WSe2-MoSe2-EG Synthesis 125
7.2.3 Materials Characterization 126
7.2.4 Theoretical Methods 127
7.3 Results and Discussion 127
7.3.1 Making Vertical vdW Heterostructures 127
7.3.2 2D Alloys on a Non-vdW Substrate 129
7.3.3 The Interlayer Coupling Within 2D Junctions 130
7.3.4 Vertical Electrical Transport 132
7.3.5 NDR in vdW Heterostructures 133
7.4 Conclusions 134
References 134
Chapter 8: Summary 137
Vita 139
Education 139
Research Experiences 139
Teaching and Mentorship 140
Award 140
Selected Publications 140
Appendices 142
Appendix A 142
Parameters of MOCVD Process for Epitaxial WSe2 142
Theoretical Modeling 143
Device Fabrication 144
Appendix B 145
Computational Methods for the Intrinsic Dipoles Between WSe2 and Graphene 145
Computation of WSe2 Doping Density and Charge Densities and Dependence on Parameters 146
Appendix C 148
Theoretical Validation for NDR Transport in the Trilayer Structures 148
References 150