Influence of gamma-irradiation on the optical and structural properties of Se₈₅Te_15-xBi_x nano-thin chalcogenide films

In this work, bulk Se₈₅Te_15-xBi_x chalcogenide glasses were synthesized by melt quenching technique. The nano-thin chalcogenide films of Se₈₅Te_15-xBi_x alloys with thickness 40 nm were deposited on glass/Si wafer by Physical Vapour Condensation Technique (PVCT). Their optical and structural properties were analysed by the exposure of different gamma irradiation doses. High resolution X-ray diffraction (HRXRD) and field emission scanning electron microscopy (FESEM) were used to demonstrate the crystalline and morphological properties. The phase transformation studies of nano-thin films were carried out before and after irradiation by 3, 6, and 9 kGy doses of gamma (γ) rays. The optical parameters such as absorption coefficient, Urbach tail and extinction coefficient were found to be varied with the gamma irradiation doses. Importantly, the indirect allowed band gap increased as increasing the gamma irradiation doses. These notable shifts in the optical band gap and absorption coefficient values can be explained by the increment in disorderness and lattice strain due to gamma irradiation.