Study On Electronic Structures And Optical Properties Of Two-dimensional SnS₂-based Ternary Alloys

With the unique and excellent characteristics of graphene,similar two-dimensional semiconductor materials have been an important research subject in the relevant theoretical and experimental works because of their many applications in optoelectronic devices.In addition,it has been confirmed in practical applications,the properties of several two-dimensional material is much better than their original three-dimensional compounds.For example,related theoretical calculation shows that the luminescence quantum efficiency of monolayer Mo S₂ is 10⁴ times than that of the 3-D bulk material.Monolayer SnS₂,a member of the two-dimensional semiconductor materials,has caused everybody's special attention because of its moderate band gap,flat nature,lower environmental toxicity and abundance.Recent studies show that monolayer SnS₂ can be used as lithium ion battery anode materials,phototransistor and photocatalyst for solar water splitting.At the same time,some simple binary and ternary alloy,such as SnS and FeS₂,have caused wide public concern in photovoltaic research.So in this paper,we will study the rich,environment friendly two-dimensional semiconductor material SnS₂ nanosheet using the first-principles method based on density functional theory,through doping with metal atoms in two-dimensional Sn S₂ nanosheet,adjusting and researching its electronic structure and optical properties.The main research content is as follows:1)In the research of regulating and controlling the electronic structure and optical properties via doping with different concentrations of Ti?Zr?atoms in two-dimension SnS₂ nanosheet,numerical results show that the Ti?Zr?atoms insteading of Sn atoms has obvious effects on the band gap value and optical absorption properties of SnS₂.The band gap value of Sn_1-xTi?Zr?_xS₂decreases when the doping concentration of Ti?Zr?atoms increases.And when the doping concentration of Ti atoms is 0.04,the band gap value of Sn_1-x-x Ti?Zr?_xS₂ changes from 1.59 eV to1.16 eV.This caused the significantly enhance of light absorption in the visible light range.In addition,the static dielectric constant increases as Ti?Zr?atoms doping concentration increases.The results are very beneficial for understanding the structure,electronic and optical properties of Sn_1-xTi?Zr?_xS₂ alloy.2)We explore and analyze the electromagnetic and optical properties of Cu atoms doped SnS₂ nanosheet.After simulating and caculating the structure of Sn_1-x?Cu?_xS₂,we find that the Cu atoms doped Sn_1-x?Cu?_xS₂ systems change from the magnetic ground state into a magnetic system,in spite of doping one or two Cu atoms of different configuration in SnS₂ nanosheet.For doping a Cu atom in SnS₂ nano film,we also caculated the dielectric function properties of the Cu atoms doped Sn_1-x?Cu?_xS₂ system.The data results show that the static dielectric constant of Sn_1-x?Cu?_xS₂system gradually increase when the doping concentration of Cu atoms in two dimensional SnS₂nanosheet increases.Also,the numerical results of the dielectric function light absorption intensity of the Sn_1-x?Cu?_x S₂ system have been obviously improved.Cu atoms doped Sn_1-x?Cu?_xS₂ system,compared with pure SnS₂ nanosheet,there are many new optical absorption peaks.It is very helpful for two dimensional material to absorb sunlight in the visible light range.