Fabrication And Physical Properties Of HfTe₃ Twodimensional Atomic Crystals And Related Heterostructures

The research of the two-dimensional atomic crystals has been of concern all over the world,with the discovery of graphene and its novel properties as a new type of twodimensional atomic crystals.After graphene,the discovery and research on graphenelike materials such as silicene and germanene,as well as the six party boron nitride and transition-metal dichalcogenides promote the development of the study on twodimensional atomic crystals furtherly.In this thesis,the main content is to study the growth process and physical properties of some new two-dimensional atomic crystals and heterostructures systematically.?1?It is inevitable to introduce stress which will lead to make change of the topography and electronic properties in the films,during the epitaxial growth of films,.This thesis mainly studied the wrinkles of HfTe₃ films which are caused by the lattice mismatch between the HfTe₃ film and substrate,during the growth of HfTe₃ films on Hf?0001?.Because its rectangular symmetry,the HfTe₃ film will produce wrinkles along a single direction.We studied the structure and properties of HfTe₃ films by XPS,STM and STS.Our results show that the lattice mismatch between the HfTe₃ film and substrate leads to special one-dimensional wrinkles on the film.And the electrical properties of these dimensional structures may be used for the development of new nanoelectronic devices.?2?It is well known that the pressure has a great influence on the superconducting properties of superconductors.Compared to bulk materials,2D materials are more likely to be compressed and folded with pressure.So 2D superconductors provide a platform for studying the relation between superconducting properties and stress.In this thesis,we studied the growth of ZrTe₃ films on Zr?110?and Zr?0001?single crystals.We confirmed the structures of the ZrTe₃ films on Zr?110?and Zr?0001?by STM and XPS.And we study the superconducting properties of ZrTe₃ thin films by STS and BCS fitting,we obtained two superconducting films with different superconducting properties.Our analysis of the experimental results show that ZrTe₃ films on Zr?110?and Zr?0001?has with different characteristics of stress,which caused by different symmetry two single crystal substrate.However,this small difference will lead to significantly different superconductivity properties.The results show that we can use the stress to artificially adjust the superconducting properties,and we provide a new way for adjusting two-dimensional superconducting materials and related superconducting devices.?3?In recent years,two-dimensional heterostructures showed their unusual characteristics and new physical phenomena,such as Hofstadter's buttery.In addition,another interesting physical phenomena,Majorana fermions,is predicted to be found in the heterostructures composed of superconductor?SC?and topological insulator?TI?.Majorana fermion is a predicted eighty years ago,and its antiparticle is itself.This chapter reported that a HfTe₃-HfTe5 heterostructure was prepared on a Hf?0001?single crystal by the method of MBE.And we characterize the properties of the heterostructure with STS.First of all,the tellurium atoms were deposited onto the substrate directly when the hafnium substrate is at the temperature of 500 °C.The tellurium atoms and the hafnium atoms from substrate would be synthesized into HfTe5.Then,we stopped the deposition of tellurium atoms when the hafnium substrate is at the temperature of 560 °C.The top layers of HfTe5 would be decomposed into HfTe₃,and we got a HfTe₃-HfTe5 heterostructure.The HfTe₃ is a kind of superconductor,and the HfTe5 film is predicted to be a kind of two-dimensional topological insulator.Therefore,this work opens a door for finding Majorana fermions,as well as provides a new method for the preparing superconducting devices.?4?The phonon-electron interaction has attracted wide attentions in low dimensional systems.Superconductivity and charge density wave?CDW?are both the result of the phonon-electron interaction.In this chapter,we prepared a TiTe2 film on Ti?101????for the first time with the method of MBE.And we use XPS and STS to confirm the structure of the TiTe2 film.Based on our experimental observations,we find that the TiTe2 film has the properties of superconductivity and CDW.It provides a perfect platform for the study of the phonon-electron interaction in low dimensional systems.