First-principles Study On Electron-phonon Interaction In Electrical And Thermal Transport Properties For Two-dimensional Materials

Two dimensional(2D)materials have attracted great attentions in recent years owing to their excellent electrical,optical,and thermal properties,and they are widely applied to many important fields,such as electronic devices,new energy,environmental protection,biomedical and so on.In this dissertation,based on density functional theory combined with Boltzmann transport equations(BTE),electron-phonon interaction(EPI)which was beyond the deformation potential approximation,as well as electrical and thermal transport properties for 2D nanomaterials were comprehensively investigated from first-principles study with the maximally localized Wannier interpolation technology.We try to explore the internal physical factors and gain the deep insight to improve electrical and thermal performance for 2D functional materials with state-of-the-art theoretical calculations.In the first part of the dissertation,the phonon limited electrical transport properties were calculated for 2D materials.Firstly,we studied the electron mobility of different types of graphynes.Due to unique electronic band structures with Dirac cone,graphynes act out outstanding electrical transport properties.The electron mobilities for all graphynes exceed 10³cm²/V·s at 300 K from our prediction,and it is found the acetylenic linkage limited group velocity and E_2g phonon modes limited relaxation times are the underlying reasons of determining electron mobility for these Dirac materials.Furthermore,we considered the Fr(?)hlich interaction in polar semiconductor,and systematically studied the Fr(?)hlich interaction and intrinsic carrier mobilities for polar semiconductor In X(X=S,Se,Te).It shows that In Te is a potential high mobility electronic material,and it is revealed that the weak polar 2D materials with single valley tend to have higher mobility,which provides a meaningful way to find high mobility2D semiconductor materials.In the second part of the dissertation,we further studied the effect of EPI on thermal transport properties for 2D materials,on the basis of three phonon scattering.Firstly,taking MoS₂ and Pt SSe as examples,the lattice thermal conductivities of doping 2D semiconductors were studied.It shows that EPI has a significant reduction on phonon lifetime and lattice thermal conductivity.The higher the doping carrier concentration is,the lower the thermal conductivity would be,and we find that temperature dependent lattice thermal conductivity deviates from T^-1.Our research makes great sense of accurate heat conduction properties prediction for heavily doped 2D materials and the interpretation of the lattice thermal conductivity in experimental measurements.In addition to electron limited phonon lifetime,we studied hole doping induced phonon frequency renormalization.When hole doping concentration reaches-0.01 e/u.c.(?7.1×10¹²cm^-2),it finds that the room-temperature lattice thermal conductivity is prominently reduced as much as 27%due to phonon softening effect,and total 32%reduction is obtained after considering EPI limitation on phonon lifetime.Besides,with the increase of hole doping level,the softening effect on the lattice thermal conductivity become more striking,which provides a new perspective to reduce the lattice thermal conductivity for 2D materials.