Optical properties of amorphous Ge30-xSbxS70Ge30-xSbxS70 films

We have analyzed the optical properties of a-Ge30-xGe30-xSbxS70SbxS70 chalcogenide glass films (x=0,10,20(x=0,10,20 and 30 at%); the chalcogenide films were prepared by vacuum thermal evaporation. The optical-absorption data indicate that the absorption mechanism is non-direct transition. We found that the optical band gap, EoptEopt, decreases from 2.04±0.012.04±0.01 to 1.74±0.011.74±0.01 eV, whereas the refractive index increases with increasing Sb content. Data are analyzed by the Wemple equation, which is based on the single-oscillator model.