Dispersive optical constants of a-Se100-xSbx films

Thin films of amorphous Se100-xSbx (x=5, 10 and 20 at%) system are deposited on a silicon substrate at room temperature (300 K) by thermal evaporation technique. The optical constant such as refractive index (n) has been determined by a method based on the envelope curves of the optical transmission spectrum at normal incidence by a Swanpoel method. The oscillator energy (E-o), dispersion energy (E-d) and other parameters have been determined by the Wemple-DiDomenico method. The absorption coefficient (alpha) has been determined from the reflectivity and transmitivity spectrum in the range 300-2500 nm. The optical-absorption data indicate that the absorption mechanism is a non-direct transition. We found that the optical band gap, E-g(opt), decreases from 1.66 +/- 0.01 to 1.35 +/- 0.01 eV with increase Sb content. (C) 2003 Elsevier Ltd. All rights reserved.