INVESTIGATION OF OPTICAL CONSTANTS AND OPTICAL BAND GAP FOR AMORPHOUS Se40-xTe60Agx THIN FILMS

This paper report the effect of silver (Ag) content on optical properties of amorphous chalcogenide glasses Se40-xTe60Agx (x = 0, 2, 4, 6, 8). Thin films of a-Se40-xTe60Agx glassy alloys have been synthesized by thermal evaporation technique under high vacuum conditions (similar to 10(-5) torr). The optical spectra of amorphous Se40-xTe60Agx (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 200-3000 nm. Swanepole technique has been used to calculate the optical constants [refractive index (n), extinction coefficient (k), real dielectric constant (epsilon '), imaginary dielectric constant (epsilon '') and absorption coefficient (alpha)] and optical band gap of amorphous Se40-xTe60Agx thin films. Absorption coefficient (alpha) increases with incident photon energy (hv) for all the samples. The optical band gap increases with increase of the silver (Ag) content. The increase in optical band gap with increase of the Ag content has been explained on the basis of Mott and Davis Model.