The Study Of Physical Properties And Heterostructure Design Of Planar Stanene

Two-dimensional materials are key materials in the industry such as optoelectronics,microelectronics and energy,and their abundant material systems and novel physical properties have received extensive attention and research.Among them,stanene,as a type of graphene-like material,has more advantages than graphene,but it has a buckled height in the third direction.As a functional material derived from stanene,planar stanene has a zero-buckling honeycomb-like structure with a unique large band gap characteristic presenting two-dimensional topological insulator properties,provide opportunities for applications in higher integrated devices with two-dimensional topological properties in electronics and quantum fields.At present,there is little research based on planar stanene,although there is some theoretical and preactical work,their fundamental physical properties,composite structures and device applications need to be further investigated in depth.The main research and innovations in this thesis include:(1)Structural characterisation and topological properties of functionalised planar stanene.This thesis focuses on the geometrical,electronic and topological properties of single-and double-sided functionalised models of planar stanene.It is shown that the energy band structures of s-SnF,s-SnCl and s-SnBr have an s-p energy band inversion at the Γ point.When spin-orbit coupling(SOC)is considered,there is a transition from semi-metallic to semiconducting properties with a maximum band gap of 0.25 eV.Theoretical calculations predict that s-SnF,s-SnCl and s-SnBr are topological insulators,and this conjecture is verified with the aid of nanoband edge states.It is thus shown that planar stanene with passivated halogen atoms can achieve topological phase transitions and can effectively control Quantum Spin Hall states.(2)Study of exciton effects and optoelectronic properties of planar stanene.By calculating the quasiparticle band gap,spectral absorption peaks and exciton binding energy,focusing on single-and double-sided passivation of planar stanene.The quasiparticle band gap of 2.95 eV and high exciton binding energy of up to 1.66 eV were found to exhibit strong exciton effects.This thesis innovatively extends the first principle multi-body perturbation theory(MBPT)optimization method,based on the GW approximation and BSE,to determine the bound and resonant excitons in passivated planar planar stanene by introducing the random phase approximation(RPA)and SOC to optimize the quasi-band gap and absorption spectra.(3)Study of the planar stanene heterostructure system.In this thesis,the heterostructures of planar stanene/MoS2 and planar stanene/4-SiC were modelled,and their geometrical and electronic properties were investigated based on different modulation methods.It is found that the extension of the stanene from a buckled to a planar structure is caused by a combination of pz orbital filtering and tensile stress.The different bonding types(van der Waals interaction/chemical bonds)between planar stanene and the two substrates are clarified through calculations,and the topological property change patterns of planar stanene/MoS2 heterostructures and planar stanene/4-SiC heterostructures are revealed.Low mismatch planar stanene heterostructure designing method is studied:Based on 4-SiC and MoS2,a planar stanene heterostructure with a lattice mismatch of less than 5%was constructed,and the formation of planar stanene in the heterostructure was found to be a combination of pz orbital filtering and tensile stress.Calculations revealed that the topological properties of stanene/MoS2 were maintained based on van der Waals interactions.Chemical bonding on the SiC heterojunction changed the topological properties of stanene.(4)Study of two-dimensional Sn-X(X=C,Si,Ge)structures in the application of electrode materials for metal ion batteries.The applicability of the two-dimensional Sn-X structure as an electrode material for lithium/sodium ion batteries was explored in this thesis.The twodimensional Sn-C system exhibits a planar structure,while the twodimensional Sn-Si and Sn-Ge systems exhibit a buckled structure.The sodium and lithium atom adsorbed two-dimensional Sn-X(X=Si,Ge)showed metallic property.The average open-circuit voltages of lithium on Sn-Si and Sn-Ge are 0.63 and 0.62 V,respectively.The average opencircuit voltages of sodium on the Sn-Si and Sn-Ge structures are 0.28 V and 0.33 V,respectively.The lithium ion storage capacities of the Sn-Si and Sn-Ge structures are 1059.7 and 840.7 mA h/g,respectively;the Sn-Si and Sn-Ge By calculating the diffusion paths of lithium and sodium ions on the Sn-Si and Sn-Ge surfaces,the results obtained indicate that the diffusion potential barriers of the Sn-Si and Sn-Ge structures are considerably low.The main innovations of this paper include:Optimised mechanism of multiple ion adsorption sites in the Sn-X(X=C,Si,Ge)lattice of stanine.The Sn-Si/Ge system of the main reasons for the high theoretical capacity:(1)the presence of a large quantity of stable ion adsorption sites in the lattice;(2)the Sn-Si/Ge structure provides a triple layer of ion adsorption,which greatly increases the storage capacity.