Photo-induced changes in arsenic selenide films

The spectral dependence of the transmittance and reflectance of thermally-evaporated amorphous AsxSe100x (where x = 20 and 40 at.%) films was measured in the wavelength range of 190 - 900 nm. A procedure was given for accurate determination of the film thickness using a standard method of numerical differences from the experimental data. The process of indirect electronic transitions was found to be responsible for the photon absorption. The variation of the energy band gap with the exposure time was investigated. Amorphous-crystalline transformations occurring as a result of photoexposure have been confirmed by the structural studies of the As20Se80 specimens using the scanning electron microscope and transmission electron microscope. Photodarkening relaxation under light exposure of the well annealed films was studied and the relaxation process has been described by the stretched exponential function (SEF).