INVESTIGATION OF OPTICAL CONSTANTS AND OPTICAL BAND GAP FOR AMORPHOUS Se70Te30-xSbx THIN FILMS

In this paper, the effect of antimony (Sb) content on optical properties of amorphous Se70Te30-xSbx thin films has been studied. Thin films of Se70Te30-xSbx glassy alloys have been synthesized by thermal evaporation technique under high vacuum conditions (similar to 10(-4) Pa). The optical transmission spectra of amorphous Se70Te30-xSbx (x = 0, 2, 4, 6, 8) thin films have been measured by a double beam UV-VIS-NIR computer controlled spectrophotometer in the wavelength range 400-3300 nm. Swanepole method has been used to calculate the optical constants (refractive index (n), extinction coefficient (k), real dielectric constant (e.), imaginary dielectric constant (e..) and absorption coefficient (a)) and optical band gap of amorphous Se70Te30-xSbx thin films. Absorption coefficient (a) increases with incident photon energy (h.) for all the samples. The optical band gap decreases with increase of the antimony (Sb) content. The decrease in optical band gap with increase of the Sb content has been explained on the basis of Mott and Davis Model.