Variation of the absorption spectra and optical energy gap with γ-ray irradiation and heat treatment in SbNbO 4 films deposited on MgO and quartz substrates

Abstract

The effects of both γ-rays irradiation and annealing temperature on the optical absorption spectra of SbNbO 4 films deposited on MgO or quartz substrates in the spectral range 190–800 nm were studied. The dose of γ-ray irradiation was varied up to 100 kGy and the annealing temperature was varied up to 900 °C. The transmittance and the reflectance were measured and hence the absorption coefficient was estimated. Annealing and γ-rays irradiation changed the general level of absorption in the treated films. A number of bands show a continuous shift in position and decrease in intensity with increasing γ-dose. The allowed optical transitions were found to be indirect transitions, hence values of the allowed indirect optical energy gap was calculated as a function of γ-dose and heat annealing temperature. The results can be discussed on the basis of γ-irradiation-induced defects in the film and on the film microstructure. The optical parameters of SbNbO 4 films are affected by the kind of substrate. The effect is more pronounced in case of films deposited on quartz substrates.