Band gap, electronic and optical properties of Zn_1-xCr _xS: An ab initio study

The band structure, electronic and optical properties of Zn _1-xCr_xS (x = 0-1) are studied by spin-polarized first-principle calculations. The results show that Zn_1-xCr _xS display half-metallic characteristics. The band gap of minority spin increases from 2.098 eV to 3.98 eV with Cr component, while the half-metallic gap decreases from 0.992 eV to 0.548 eV. Both the static dielectric constant ^ε1(0) and static refractive index n(0) increase with Cr component, but the increment is slowed down for Zn _0.5Cr_0.5S as a result of lowered crystal symmetry. New absorption peaks appear in the energy range of 0-2.83 eV and 38.45-65.04 eV due to doped Cr, moreover, the peak intensity is enhanced with the increasing Cr component and the absorption peaks have a blue shift slightly. The extinction coefficient k(ω) in the energy range of 2.83-20 eV decreases with the increase of Cr component. The results provide useful theoretical guidance for the application of Zn_1-xCr_xS in optical detectors and spintronics.