MoS_(2)光学性质的第一性原理计算

First principles calculation of optical properties of MoS_(2)

为研究不同层数MoS_(2)的光学性质以及缺陷对单层MoS_(2)光学性质的影响,利用基于密度泛函理论的第一性原理,计算1~3层MoS_(2)的能带结构、拉曼光谱和光学性质以及具有空位缺陷的单层MoS_(2)的拉曼光谱和光学性质.研究结果表明:单层MoS_(2)为直接带隙半导体,而2~3层MoS_(2)为间接带隙半导体.对于1~3层MoS_(2)的拉曼光谱,随着层数的减少,约在380 cm^(-1)处的拉曼峰会发生蓝移,约在400 cm^(-1)处的峰值发生红移.对于含有空位缺陷的单层MoS_(2),Mo空位的拉曼峰出现在369、389和401 cm^(-1)附近,而464 cm^(-1)处的拉曼峰是S空位的标志.为了进一步确定构型的产生,计算出S空位的形成能为2.69 eV,Mo空位的形成能为7.98 eV.对于介电函数的虚部,缺陷单层MoS_(2)与1~3层MoS_(2)的介电函数虚部具有相似的外形,但由于空位缺陷的局域效应,缺陷单层MoS_(2)的介电函数虚部发生略微红移.

In order to study the optical properties of different layers of MoS_(2)and the influence of defect monolayer MoS_(2)on its optical properties,the first principles based on density functional theory were used to calculate the band structure,Raman spectrum,optical properties of 1-3 layers of MoS_(2)and Raman spectrum and optical properties of monolayer MoS_(2)with vacancy defect.The results show that single-layer MoS_(2)is a direct band-gap semiconductor,while 2-3 layers MoS_(2)is an indirect bandgap semiconductor.For 1-3 layers of MoS_(2)Raman spectrum,the peak value at about 380 cm^(-1) will be blue shift,and the peak value at about 400 cm^(-1) will be red shift with the reduction of the number of layers.For the monolithic MoS_(2)Raman spectra with vacancy defects,the Mo vacancy Raman peak appears near 369 cm^(-1),389 cm^(-1),401 cm^(-1),and the Raman peak at 464 cm^(-1)is the symbol of the S vacancy.In order to further determine the formation of the configuration,the formation energy of the S vacancy is 2.69 eV and that of the Mo vacancy is 7.98 eV.For the imaginary part of dielectric function,the defect monolayer MoS_(2)has similar appearance with the imaginary part of dielectric function of 1-3 layers MoS_(2),but due to the local effect of vacancy defect,the imaginary part of dielectric function of defect monolayer MoS_(2)has a slight red shift.