Design And Physical Properties Of Two-Dimensional Stanene And Its Heterostructures

Two-dimensional(2D)materials have attracted wide attention due to their potential applications in optoelectronic,microelectronic,and energy materials and related devices.Stanene and graphene are both IV-nene.In 2013,Professor Shoucheng Zhang predicted that 2D stanene is a quantum spin Hall(QSH)insulator,which have practical applications at room temperature.This stimulated the researches about stanene.In theoretical,the researchers explored the fundamental physical properties of stanene and found many novel characteristics.In the experiment,the researches mainly focused on the growth of single layer stanene.This thesis comprehensively investigated the mechanical properties,many-body effect,heterostructures,and applications in energy materials of stanene.The main research contents of the thesis include:(1)Research on the geometric structures and mechanical properties of stanene.The ideal strength and high-order elastic constants of stanene were studied.The results show that Young's modulus of stanene is the smallest among all the ?-nene,which indicates that stanene is the most easily strained,meaning the electronic properties of stanene can be easily tuned by the strain.Furthermore,we investigated the effect of three kinds of strain,equiaxial(EQ)strain,uniaxial armchair(AC)strain and uniaxial zigzag(ZZ)strain,on the geometric properties of stanene and hydrogenated stanene(stanane).(2)Research on the electronic properties,many-body effect and optical properties of stanene and stanane.Considering the effect of many-body effect,spin-orbit coupling(SOC)and strain on the electronic and optical properties of stanene and stanane,different calculation levels(GW,GW+RPA,GW+BSE,GW+RPA+SOC,GW+BSE+SOC)were used.The accurate quasi-particle(QP)band gap,optical absorption peak,and exciton binding energies were obtained.The QP band gap of stanene and stanane are 0.10 and 1.63 eV,respectively.The bound and resonance excitons are located at 1.54 and 3.50 eV with the corresponding exciton binding energies of 0.09 and 0.61 eV,respectively.(3)Research on the 2D stanene heterostructures.The geometric and electronic properties of stanene/graphene and stanene/MoS2 were studied.Both stanene and graphene have Dirac points,which make the stanene/graphene heterostructures exhibit the novel electronic properties.When the two Dirac points located at the same high-symmetry point,there occurs the band irnversion.By calculating the topological invariant Z2,the topological state was determined.Furthermore,the band gaps of the heterostructures can be tuned by the external ways such as strain and electric field.(4)Research on the application of stanene nanomesh(SnNM)as energy materials.By designing the structures of SnNM,the performance of SnNM as an anode material of sodium ion batteries was investigated.Compared with stanene,SnNM can increase the binding energy with Na ions,increase the maximum theoretical capacity(up to 60%),and provide new diffusion paths.The results show that SnNM can be a potential anode material for sodium ion batteries,and the inducing of nanomesh can be an effective way to improve the performance of 2D materials in metal ion batteries.The main innovations of the thesis include:(1)The many-body perturbation theory based on the GW approximation and Bethe-Salpeter equation(BSE)is developed.Random phase approximation(RPA)and SOC are induced to correct the QP band gap and optical absorption peak.The bound exciton and resonance exciton of stanane are determined by this way.(2)Based on the hexagonal structures of stanene and graphene,the specific expansion ratio((?),m and n are integers)of the primitive cell is used to screen out the heterostructures with the lattice mismatch less than 4%,and the minimum lattice mismatch is low up to 0.07%.Besides,the calculation of topological invariant Z2 is applied to the heterostructures.(3)The evolution law of multi vacancies recombination of stanene was studied and the formation process of SnNM was proposed.Furthermore,the application of SnNM as an anode material for sodium ion battery was investigated,which can provide a guide for the practical application of stanene.