Influence of X-ray Irradiation on Optical Parameters of (Ga0.2 In0.8)2 Se3 Films

$\left(G a_{0.2} \operatorname{In}_{0.8}\right)_{2} \mathrm{Se}_{3}$ films were deposited by the thermal evaporation technique. As-deposited thin films were irradiated using wideband radiation of Cu-anode X-ray tube at different exposition times. The spectral dependences of refractive index and extinction coefficient were measured by the spectral ellipsometry technique. The optical transmission spectra of X-ray irradiated $\left(G a_{0.2} \operatorname{In}_{0.8}\right)_{2} \mathrm{Se}_{3}$ films were studied depending on irradiation time. Parameters of Urbach absorption edge for X-ray irradiated $\left(G a_{0.2} \operatorname{In}_{0.8}\right)_{2} \mathrm{Se}_{3}$ films were determined. The nonlinear decrease of energy pseudogap as well as nonlinear increase of Urbach energy and refractive index with increase of X-ray irradiation time are revealed. The spectral dependences of refractive indices of non-irradiated and X-ray irradiated $\left(G a_{0.2} \operatorname{In}_{0.8}\right)_{2} \mathrm{Se}_{3}$ films are described by different dispersion relations.