Electronic Transport Of Several Two-dimensional Transition-metal Dichalcogenides

Exploration and understanding of nanomaterials has deepended with the rapidly development of science and technology.A series of two-dimensional structural materials with excellent electrical properties such as graphene and transition metal-sulfur compounds have been discovered,electronic devices with excellent properties are being designed and manufactured.With the development of experimental preparation technology and synthesis technology,two-dimensional structural materials have shown great application potential in terms of structure and electronic properties'regulation.Two-dimensional transition metallothionides exhibit many peculiar electrical properties,and their unique"sandwich"structure provides possibilities for the regulation of electronic properties.Recently,a series of new structures,such as Janus structure,which is different from the traditional transition metal-sulfur group compounds,have been synthesized experimentally,showing excellent electrical properties and broad application prospects.In the present thesis,the electronic structure and transport properties of several special two-dimensional transition metallothionides are studied by combined density functional theory with non-equilibrium Green's function,and the intrinsic physical mechanisms behind the phenomena are revealed.The main contents are as follows:The electronic structure and transport properties of two-dimensional Janus transition metal-sulfur compounds were studied.It was found that there was a metal-semiconductor transition between OMo Te structure and its parent structures?Mo O₂ and Mo Te₂?.Gradually increasing the oxygen atom doped concentration realizes the gradual transition from metal to semiconductor,which provides a new way to regulate the electronic structure of the system.The influence of external stress on the electronic properties of anisotropic two-dimensional Re S₂ structure was studied.The stress leads to the metal-semiconductor transformation of Re S₂,and the structure is sensitive to compressive stress,but non-sensitive to tensile stress.The tensile stress does not trigger the metal-semiconductor transition in Re S₂,different from isotropic transition metal sulfides.Further analysis shows that the bond of metal-metal atom and anisotropic of interaction force are the mechanisms for the different behaviors of structure in compress/tensile.The study on electronic structure and transport properties of multiple doped in two-dimension transition metal dichalcogenides were performed.It was found that the doped isomers show different electronic properties:OMTe,OMNTe?M,N=Cr,Fe,Mo,W?exhibit metallic?except1OWTe?,while 1OWTe exhibit semiconducting.With the analysis of the bond length,it is found that there exists threshold bond length,corresponding to the transition of electronic properties.And the variations in the strength of interactions between atoms lead to differences in the electronic properties.