Transport Properties Of Silicene And TaAs Heterojunction

This thesis mainly studies the quantum transport properties of two-dimensional materials,the research materials are silicene and the first type Weyl semimetal TaAs.The two materials selected in this thesis have the same cross-type energy band as graphene.In the study,the energy bands of these two materials are opened up,so that the transport properties of materials with a cross-type energy band structure can be adjusted by adjusting the energy gap.It is possible,which has important research significance in studying the transport properties of low-dimensional material devices,and also provides a theoretical basis for the production of actual devices..In this thesis,the transport model is calculated and simulated using Nanodcal software package.This thesis makes a detailed analysis of the research situation,model building and theoretical calculation of silicene and TaAs.Chapter ? introduces some interesting properties and the research status of silicene and TaAs,and then discusses the significance of researching these two materials.Chapter ? introduces the first principles,DFT and NEGF.Then we introduce the software package Nanodcal which based on these methods.The calculation method and processing skills used in the thesis,and the derivation process of the calculation are given.Chapter ? describes two work done by the author.The first work studied the influence of the strain,electric field and electric potential on the valley-polarized transport properties of the silicene narrowed nanoribbons.In this work,different amplitudes of the strain,applied electric fields and potentials were applied to the silicene nanoribbons.The effects of parameters on the valley-polarized transport properties of the silicene nanoribbons were calculated.The results illustrate that the strain has little effect on the energy band.The electric field enables the energy band to open a band gap and induces the phenomenon of zero conductance,which eliminates the spin degeneracy of the energy band.The nature of transport has a greater regulatory role.The second work studied the modulation of the strain on the transport properties of TaAs.In this work,strains in different directions were applied to the TaAs,and the effect of strain on the transport properties was analyzed.According to energy band structures of TaAs,the Weyl point of TaAs is destroyed under the action of the strain.As the amplitudes of strain intensity increases,a new Weyl point can be formed.Subsequently,the transmission coefficient of the TaAs heterojunction was obtained,and the strain resistance was introduced to describe the modulation of the strain on the system's transport properties.The results illustrate that the strain applied along the vacuum direction of the device decreases the conductance of the device with the increasing of in the strength,while the strain applied along the periodic direction induces negative strain resistances,and the conductance is not significantly reduced.The strain-induced transport behaviors in in TaAs heterojunctions have an important theoretical meaning for the next generation of the TaAs-based nanodevices.Chapter ? summarizes our research work done and analyzes its physical meaning.Chapter V discusses the follow-up research ideas of TaAs systems and analyzes the application prospects of the transport software package of Nanodcal.