The electronic, magnetic and optical properties of single-layer CrS2 with vacancy defects

Based on the first-principles calculations, we have systematically studied the electronic, magnetic and optical properties of single-layer CrS2 with and without vacancy defects. The S vacancy is the most energetically favorable vacancy among the considered S vacancy, Cr vacancy, S-2 double vacancy and CrS double vacancy. The vacancy induced defect states drop into the original band gap region, so the smaller band gaps have been obtained for single-layer CrS2 with vacancies compared with the perfect one. Although the perfect single-layer CrS2 is a nonmagnetic direct band gap semiconductor, the magnetic semiconductor is obtained via either Cr vacancy or CrS double vacancy. The S vacancy and S-2 double vacancy are still nonmagnetic semiconductors with reduced band gaps. Furthermore, the static dielectric constants and static refractive index of single-layer CrS2 with vacancies are all bigger than those of perfect CrS2 because the reduction of the band gaps. The first main absorption peak is weakened while the other two main peaks are all significantly enhanced for single-layer CrS2 with vacancies.