Optical properties change in laser-induced Te/As₂Se₃ chalcogenide thin films

In the present work, we report the change in optical parameters due to the deposition and photo-induced diffusion of Te layer into the chalcogenide As₂Se₃ film. The photo-diffusion creates a solid solution of As-Se-Te which has potential application in optical devices. The Te/As₂Se₃ bilayer films prepared by thermal evaporation technique were studied by various experimental techniques. The photo-diffusion of Te into As₂Se₃ matrix was done by 532-nm laser irradiation. The structure of the As₂Se₃, as-prepared and irradiated Te/As₂Se₃ films was studied by X-ray diffraction which were amorphous in nature. The presence of all the elements was checked by energy-dispersive X-ray analysis, and the optical transmission spectra were recorded by Fourier transform infrared spectrometer. The optical band gap is reduced by the deposition and diffusion of Te into As₂Se₃ film which is due to the increase in density of defect states in the gap region. The transmission is decreased, whereas the absorption efficiency is increased with the increase in disorderness. The X-ray photoelectron spectroscopy carried out on these films gives information about the bonding change due to the photo-diffusion process. Therefore, this is an important result which will open up new directions for the application of this material in semiconducting devices. (orig.)