Fabrication and Physical Properties of Novel Two-Dimensional Crystal Materials Beyond Graphene: Germanene, Hafnene and PTSE2

Description

This thesis reports on essential experimental work in the field of novel two-dimensional (2D) atomic crystals beyond graphene. It especially describes three new 2D crystal materials, namely germanene, hafnene, and monolayer PtSe2 fabricated experimentally for the first time, using an ultra-high vacuum molecular beam epitaxy (UHV-MBE) system. Multiple characterization techniques, including scanning tunneling microscope (STM), low energy electron diffraction (LEED), scanning transmission electron microscope (STEM), and angle-resolved photoemission spectroscopy (ARPES), combined with theoretical studies reveal the materials' atomic and electronic structures, which allows the author to further investigate their physical properties and potential applications. In addition, a new epitaxial growth method for transition metal dichalcogenides involving direct selenization of metal supports is developed. These studies represent a significant step forward in expanding the family of 2D crystal materials and exploring their application potentials in future nanotechnology and related areas. Supervisor’s Foreword Parts of this thesis have been published in the following journal articles: Acknowledgements Contents Abbreviations 1 Introduction 1.1 The Rise and Development of Graphene-Like 2D Crystal Materials 1.1.1 From Graphene to Graphene-Like 2D Crystal Materials 1.1.2 Synthesis and Characterization 1.2 Silicene and Germanene 1.2.1 Theoretical Investigations 1.2.2 Experimental Explorations 1.3 Transition Metal Dichalcogenides 1.3.1 The Rise of TMDs 1.3.2 Structural Properties of TMDs 1.3.3 Electronic Properties of TMDs 1.3.4 Synthesis of TMDs 1.3.5 Applications of TMDs 1.4 h-BN and Other Graphene-Like 2D Materials 1.5 Van der Waals Heterostructures 1.6 Research Contents and Instruments 1.6.1 Research Contents 1.6.2 Introduction of Instruments References 2 Germanene on Pt(111) 2.1 Background 2.1.1 From Silicene to Germanene 2.1.2 Early Exploration of Germanene Growth 2.2 Fabrication and Computation Methods 2.3 Structural Characterizations and Theoretical Calculations 2.4 Summary and Outlook References 3 Hafnene on Ir(111) 3.1 Background 3.2 Preparation and STM Study 3.3 Theoretical Calculations of Atomic and Electronic Structures 3.4 Bilayer Hafnene and Hafnene Grown on Other Supports 3.5 Summary and Outlook References 4 Monolayer PtSe2 4.1 Background 4.2 Growth and Atomic Structure 4.3 Electronic Structure 4.4 Photocatalytic Properties 4.4.1 Experimental Setups 4.4.2 Photocatalytic Characterizations 4.5 Valleytronics 4.6 Summary and Outlook References 5 Conclusions and Prospect