Molecular Beam Epitaxy Growth Of Graphene And Van Der Waals Heterostructures

Graphene is a honeycomb nano-material formed by a monolayer of sp2 hybridized carbon atoms,which has unique band structure,excellent physical properties and potential applications.Great interests of 2D materials have been attracted since graphene was first discovered in 2004.Van der Waals heterostructures can be formed by stacking different 2D materials on top of each other in design orders,and exhibit significantly better properties.However,controllable preparation of high-quality heterostructures is still a difficulty in this field.In this thesis,graphene and Van der Waals heterostructures were prepared by MBE growth,in a ultrahigh vacuum system integrated of molecular beam epitaxy,X-ray photoemission spectroscopy and scanning tunneling microscopy?UHV MBE-XPS-STM?.The main results are summarized as follows:1.Continuous,high-quality graphene films have been epitaxial grown on a metal Ru?0001?substrate and semiconductor 6H-Si C?0001?substrates,respectively.In-situ STM characterization showed flattern surfaces and perfect crystalline structures.2.Four types of 2D materials-Bi₂Se₃,Bi₂Te₃,MoSe₂ and MoTe2 – have been grown by MBE on graphene-terminated 6H-SiC?0001?substrates,so as to form Van der Waals heterostructures.Surface morphography,crystal structures,and chemical information of epitaxial layers were characterized by in-situ STM and XPS.What's more,high-quality MoTe₂ layer has been grown by MBE for the first time,and our STM showed atomic-resolution 1T' phase as well as some novel periodic structures.