First Principles Study On Electronic And Optical Properties Of MoS₂ And CoSb₃ Under Different Pressures

With the rapid development of science and technology,semiconductor materials have become the most important materials in the information field.It is a material with conductivity between conductor and insulator.They can be used to make semiconductor transistors,integrated circuits,semiconductor lasers and so on.Monolayer MoS₂ is a typical transition metal dihalide compound(TMDs),which has similar properties to graphene.However,MoS₂has band gap and is a direct band gap semiconductor material.Based on density functional theory,this paper studies the electronic structure,density of states,phonon dispersion relationship and Raman spectrum of 2H MoS₂under biaxial strain.The results show that the band gap,structural stability and Raman peak of MoS₂change obviously under biaxial strain.When compressed to 4%and stretched to 4%,MoS₂changes from direct band gap semiconductor material to indirect band gap semiconductor.When the strain is 10%,MoS₂can be transformed from direct band gap semiconductor material to metal material,and the band gap value decreases with the increase of stretching degree.The phonon dispersion curve is greatly affected by strain.When compressed to 4%,the phonon dispersion curve appears virtual frequency.The structure began to become unstable,and the maximum tensile degree of MoS₂was 19.5%.With the increase of stretching degree,the peak value of Raman spectrum also changes obviously.Skutterudite CoSb₃ is one of the most promising n-type skutterudite compounds.It is composed of more abundant elements than other skutterudites and less toxic elements.It is a narrow band gap semiconductor with indirect band gap.Based on the density functional theory,the lattice constant,structure volume,electronic structure,density ofStates,phonon dispersion curve,Raman spectrum and infrared spectrum of CoSb₃under different pressures are studied in this paper.In the range of 0-20 GPa,the band gap increases with the increase of applied pressure intensity,but it is still an indirect band gap semiconductor.By analyzing the phonon dispersion curve of CoSb₃,it is found that the phonon dispersion curve still has no virtual frequency and the stability of the structure has not changed when the pressure of 0-20 GPa is applied.In the process of applying pressure,the Raman spectrum and infrared spectrum have changed significantly,and the Raman frequency has a blue shift.