Transport Properties Of Low-dimensional Materials Based On Green's Function

This paper mainly studies the transport properties of two-dimensional semiconductor materials,including graphene,silicene,MoS₂ and other two-dimensional materials.The theoretical analysis and numerical calculation are adopted to study the transport properties.The actual calculation and analysis are carried out by using the software MATLAB and Nanodcal.In chapter one,several new low-dimensional semiconductor materials are introduced,including graphene,transition metal sulfides,silicene.In chapter two,we briefly summary the research methods,such as the first-principles calculation and the Green's function method.In chapter three,Klein tunneling in graphene p-n junction is further analyzed.The transport properties of graphene p-n junction under the effect of the magnetic field are calculated by using the tight-binding model and the non-equilibrium Green's function method?NEGF?.During the research process,we try to use Lorentz force image to quantitatively analyze the lateral migration of the transmission curve.Through detailedly numerical analyzing,the relationship between the transmission curves and different parameters has been obtained.In addition,the effective energy range of the tunnel effect is obtained by analyzing the motion of Dirac Fermion along the gyrotropic orbit under the vertical magnetic field in terms of the angular-dependent transmission.In chapter four,the transport properties of the silicene constriction?depressed in the center region?are also studied by using the non-equilibrium Green's function.Firstly,the energy band of the central region is calculated in the presence of the electric field.Secondly,the effect of the strain on the transport properties of silicene constrictions is discussed.The electric field can open a large band gap for the silicene constrictions.The amplitude of the band gaps depends on the amplitude of the electric field.It is found that the strain has no effect on the band gap of the silicene nanoribbon,only slightly modifies the profile of the energy subbands.Subsequently,the valley-dependent conductance and the valley polarization of the silicene constrictions are discussed under the influence of the strain and the electric field.Moreover,the combined effect of the electric field and the ferromagnetic exchange field on the transport properties is also analyzed.Finally,the self consistent of single layer MoS₂ is completed by first-principle calculation.Subsequently,the band characteristics of single layer MoS₂ were calculated.It is confirmed that the bulk MoS₂ is different from the monolayer MoS₂.The monolayer MoS₂ crystal is a kind of direct band gap semiconductor.The band gap of the monolayer MoS₂ crystal at K point is calculated to be about 1.7eV.We also studied the transport characteristics of single layer MoS₂ and compared the transmission changes under different gate voltages.