Photo and thermal induced effects on (As2S3)0.85Sb0.15 amorphous thin films

Exposure with above band gap light and thermal annealing at a temperature near to glass transition temperature, of thermally evaporated amorphous (As2S3)0.85Sb0.15 thin films were found to be accompanied by structural effects, which in turn, lead to changes in the optical properties. The optical properties of thin films induced by illumination and annealing were studied by Fourier Transform Infrared spectrometry, X-ray Photoelectron Spectroscopy and Raman Spectroscopy. Photodarkening or photobleaching was observed in the film depending upon the conditions of the light exposure or annealing. These changes of the optical properties are assigned to the change of homopolar bond densities. The photodarkening in the as-prepared film was seen at low temperature (4.2 K).

Research Highlights
► The article describes the optical properties change due to photo and thermal induced effects on optical properties of (As2S3)0.85Sb0.15 thin film.
► The reduction of optical bandgap (photodarkening) due to light illumination is due to the creation of homopolar bonds whereas increase in optical bandgap (photobleaching) due to annealing is due to the increase in heteropolar bonds.
► The optical bandgap at low temperature increases due to decrease in band tailings.
► New bonds are formed due to the chemical bond redistribution which can be observed from the XPS core level spectra and raman shift.