Transport Properties Of Several Two-dimensional Atomic Crystals Based On Molybdenum

Since the discovery of graphene in 2004,there are more kinds of layered materials,including semiconductors,metals and insulators has been discovered.For the application in semiconductor devices,the excellent characteristics of two-dimensional materials,such as high mobility,high surface area ratio and low power consumption,bring new ideas to break through the limit of Moore's law.On the other hand,with the change of material dimensions,a large number of novel physical properties emerge,such as superconductivity,Weyl semi metal,and topological insulator,which opens up a new field for theoretical research.Transition metal chalcogenides have attracted much attention due to their novel topological properties.Molybdenum telluride,as a typical transition metal chalcogenide,has three phases,including semiconductor(2H),metal(T_d)and semi metal(1T').In the past few years,three-dimensional 1T'-Mo Te₂ has been proved to be a type-II Weyl semimetal,and two-dimensional single-layer 1T'-Mo Te₂ was predicted to be a topological insulator.However,there is no research on one-dimensional 1T'-phase Mo Te₂.In this dissertation,preparation,characterization and transport properties of one-dimensional 1T'-Mo Te₂ nanowires,two-dimensional 1T'-Mo Te₂ nanosheets and their precursor,Mo O₃ single crystal,were studied.The following results are achieved:1.The preparation,characterization and field effect transistor performance of Mo O₃ are achieved.The transistor based on indium selenide(In Se)with platinum as contact shows bipolar behavior.The In Se and Mo O₃ heterojunction are further fabricated in which the forward rectifying junction,N⁺N junction can be realized by the control of gate voltage.Furthermore,the optoelectronic performance of the heterojunction has been studied.The optical/dark current ratio reaches 10⁴.The rise and fall time are measured as 500?s and 300?s,respectively.2.The successful preparation of molybdenum telluride nanowires with controllable diameter ranging from 27 to 80 nm were achieved.The structures and component were characterized by Raman,HRTEM,SAED and EDS.The transport properties of 1T'-Mo Te₂ nanowires revealed that the resistivity of shows metallic behavior and agrees well with the Fermi liquid theory(<20 K).The coherence length extracted from 1D Hikami-Larkin-Nagaoka(HLN)model with the presence of strong spin-orbit coupling is proportional to T^-0.36,indicating a Nyquist electron-electron interaction dephasing mechanism at one dimension.3.The successful preparation of 1T'-Mo Te₂ nanosheets was achieved.The structure and component of the nanosheets was characterized by Raman and STEM.The transport properties of the nanosheets showed that the nanosheets had a band gap of?10 me V at low temperature,and the linear magnetoresistance effect was found at low temperature.These results provide a feasible way to prepare one-dimensional topological materials and is promising for fundamental study of the transport properties.