Thermal Transport And Thermoelectric Properties In Two-dimensional Materials: Group-? Binary Compounds

With the miniaturization of nano-electronic devices and the development of integrated circuits,heat dissipation become an urgent problem to be solved.The study of heat transport in nanostructures has certain theoretical significance and application value.In addition,energy shortage and waste heat pollution have become important issues of great concern all over the world.The global energy market is in transition,and the need for new clean energy sources is growing.The development and application of thermoelectric materials is a new way to solve the problem of energy shortages and waste heat pollution.In recent years,two-dimensional nanomaterials have shown great potential in thermoelectric conversion due to their superior electronic and heat transfer properties.In this paper,the thermal transport and thermoelectric conversion properties of monolayer honeycomb structures of group-IV(C,Si,Ge,Sn)binary compounds are calculated.The main contents are as follows:Firstly,we have systematically studied the thermal transport properties of group-IV binary compounds by combining first-principle calculation and the phonon Boltzmann transport equation.There are several interesting phenomena:(i)the thermal conductivities(k)of these materials span so many orders of magnitude(0.04-144.29 m^-1 K^-1),which has potential application value in the field of nano-thermoelectric materials and thermal information management.(ii)thekof low-buckled(LB)structures is lower than that of planar(PL)structures(iii)thekof the binary compound composed of Sn is lower than that of the same type of the PL or LB materials.Through the comparative analysis of PL-Si C and LB-Si Sn,we found that the LB structures have heavy atomic mass and small phonon group velocity.We also investigate the contribution of different modes to thek,the results show that ZA phonons scattering of the PL structures is suppressed,which can lead to the proportion of ZA mode in thekas high as 50%.Meanwhile,for LB structures,the LA mode has a great contribution to thekdue to the scattering channels for high-frequency LA phonons are suppressed in materials with a-o gap.Secondly,on the basis of the study of thermal transport properties,the thermoelectric properties of group-IV binary compounds are studied by the first principles combined with the electron Boltzmann transport equation,and the deformation potential theory.The results show that the thermoelectric performance of low-buckled(LB)structural materials such as Si Ge,Si Sn and GeSn is better than that of planar(PL)structural materials such as SiC,GeC and SnC,which can be attributed to the narrow band gap and low lattice thermal conductivity of LB materials.In addition,LB-SiSn exhibits excellent thermoelectric properties at room temperature.Moreover,the causes of these phenomena are investigated in the paper.This work has fully studied the diversity of the thermoelectric properties of group-? binary compounds,which should be helpful to promote their novel thermoelectric applications in the future.