Theoretical investigations on the effect of defects contributes to electronic structure and optical properties of monolayer MoS2 based on first-principle calculations

In paper, for monolayer MoS₂(ML-MoS₂), five common point defect structural models are proposed, incuding two kinds of vacancy defects on the ML-MoS₂ surface with the loss of S atom or Mo atom, respectively, are denoted by V_S, V_Mo. Besides three kinds of substitution defects, Mo atom is substituted by S atoms, which is D_Mo(S), S atom is substituted with Mo atoms, which is D_S(Mo), and the defect obtained by the interchange of a pair of neighboring Mo and S atoms is denoted by D_Mo−S. Our paper aims at explore changes on electronic structures and optical properties caused by above five intrinsic defects. The hybrid exchange-correlation functional (HSE06) were used in the calculation. The results indicates compared with the intrinsic ML-MoS₂ of 5.73, static dielectric function of D_S(Mo) significantly improved, which is 7.18. For all defects models, according to density of electronic states, find their absorption peaks are all due to the electronic leaps from Mo-d orbitals to S-p orbitals and they don’t show additional absorption peaks. Due to the reflectivity decreases with the increase of photon energy around 0 ~ 0.5 eV, V_Mo and all substitution defects models, show some degradation in performance of resistance to infrared radiation. The optical conductivity imaginary part of the defective models increased in the infrared and visible regions and decreased in the ultraviolet region due to local energy levels and defect states.