Effect of γ-irradiation exposure on optical properties of chalcogenide glasses Se70S30-xSbx thin films

We investigate in the present paper the effect of the gamma-irradiation exposure by 100-500 kGy doses on the optical properties and single oscillator parameters for chalcogenide glasses Se70S30-xSbx (x=0, 12, 18 and 30 at%) thin films. These parameters were modeled from transmission spectra data measured by spectrophotometry in the wavelength range 200-2500 nm. It was found that the refractive index of the investigated films increases with increasing the doses of gamma-radiation. This post-irradiation increase in the refractive index was interpreted in terms of the increase of the density of the investigated films with irradiation due to ionization or atomic displacements. Besides, the refractive index dispersions data of both the as-deposited and gamma-irradiated Se70S30-xSbx films obeyed the single oscillator model. The calculated single oscillator parameters; oscillator strength Ea, static refractive index no, zero frequency dielectric constant epsilon(o) increased after irradiation while the oscillator energy E-o, reduced after irradiation. The absorption coefficient was found to increase with the increase of the doses of gamma-radiation. Furthermore, the obtained optical energy gap of chalcogenide glasses Se70S30-xSbx films was found to decrease with increasing the doses of gamma-radiation which is attributed to increase of the defects after irradiation. This is confirmed by the decrease in the Urbach energy E-e after radiation. The gamma-irradiation stimulated increase in the absorption coefficient and change in the optical parameters which can be utilized for industrial dosimetric purposes. (c) 2012 Elsevier Ltd. All rights reserved.