Optical properties of amorphous Ge30-xSbxS70 films

We have analyzed the optical properties of a-Ge30-xSbxS70 chalcogenide glass films (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, E-opt, decreases from 2.04 +/- 0.01 to 1.74 +/- 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. (c) 2004 Elsevier Ltd. All rights reserved.