Nanomechanical and Nanoelectromechanical Phenomena in 2D Atomic Crystals (eBook)

Nicholas Kay spent the first part of his academic career at the Physics department at Lancaster University as a joint PhD student there and at the University of Manchester through the graphene centre for doctoral training. Here he was primarily interested with the nanomechanical and nanoelectromechanical properties of 2D materials, applying scanning probe microscopy but also later surface acoustic waves and optical techniques. After finishing at Lancaster University he took a position at the National Physical Laboratory where his research now focusses on optics. He still remains active in atomic force microscopy, 2D materials and nanomechanics and nanoelectromechanics.   

Supervisor’s Foreword 8
Abstract 10
Acknowledgements 11
Contents 12
Acronyms and Symbols 15
1 Introduction 1
References 22
2 Background 24
2.1 2D Materials 24
2.1.1 Graphene 24
2.1.2 Hexagonal Boron Nitride (h-BN) 26
2.1.3 Molybdenum Disulphide MoS2 28
2.1.4 Optical Visibility of 2D Materials 29
2.2 Nanoelectromechanical Systems (NEMS) from Graphene and Other 2D Materials 31
2.2.1 Electrostatic Actuation of Graphene Resonator Devices 32
2.2.2 Damping Mechanisms Present in 2D NEMS 34
2.2.3 Beam-Membrane Mechanical Transition in 2D Materials 36
2.2.4 Characterisation of NEMS Based on 2D Materials 37
2.3 Investigating Sample Electrical and Mechanical Properties with SPM 40
2.3.1 Cantilever Dynamics 40
2.3.2 Mechanical Techniques 41
2.3.3 Electrical Techniques 43
2.3.4 Time-Resolved Techniques 47
References 50
3 Materials and Methods 54
3.1 2D Materials Preparation 54
3.1.1 Substrate Preparation and Interaction 54
3.1.2 Building Heterostructures An All-Dry Transfer of 2D Materials
3.1.3 Sample Degradation and Oxidation 56
3.2 Scanning Probe Methods 58
3.2.1 Sample Vibration 58
3.2.2 Tip Vibration 58
3.2.3 Electrostatic/Heterodyne Force Microscopy (HFM) 59
References 60
4 Morphology of 2D Materials and Their Heterostructures 1
4.1 Graphene on Hexagonal Boron Nitride 62
4.2 Graphene on Hexagonal Boron Nitride: Moirè Pattern 63
4.3 Summary 68
References 68
5 Nanomechanical Phenomena 70
5.1 Subsurface Imaging in 2D Materials with Ultrasonic Force Microscopy 70
5.1.1 Theoretical Interpretation: Sample Anisotropy 71
5.1.2 Observing Subsurface Structure in 2D Materials 75
5.2 Mechanical Properties of Graphene Grown ƒ 79
5.2.1 Stiffness Measurements of Graphene on 4H-SiC 81
5.2.2 Trapped Pockets of Hydrogen Beneath SiC 86
5.2.3 Triangular Indentations 89
5.3 Summary 92
References 93
6 Nanoelectromechanical Phenomena 95
6.1 Imaging NEMS Like Devices with Direct Contact Electrostatic Force Microscopy 95
6.1.1 Contrast Mechanism 95
6.1.2 Detecting Subsurface Charge Density Beneath Graphene 99
6.1.3 The Effect of Environmental Factors on the Operation of DC-EFM 101
6.2 Electrostatic Heterodyne Force Microscopy (E-HFM) 102
6.3 Differential Interferometry of Graphene Resonators 107
6.4 Summary 114
References 114
7 Further Work and Future Directions 116
7.1 Interaction of 2D Materials with Surface Acoustic Waves 116
7.1.1 Bilayer h-BN Resonators, Interaction with Surface Acoustic Waves and Flexoelectricity 118
7.2 High-Frequency Electrostatic Heterodyne Force Microscopy 120
References 120
8 Conclusion 122
Appendix A Materials and Methods 125
A.1 Substrate SiO2 Etching 125
Appendix B Nanomechanical Phenomena in 2D Materials 127
B.1 Growth of Graphene on SiC 127
B.2 Piezo Calibration for Differential UFM 127
Appendix C Nanoelectromechanical Phenomena 131
C.1 Electronic Detection of the Differential Interferometer Signal 131
C.2 Alignment in Differential Interferometer 131
Appendix Curriculum Vitae 133