Photo-oxidation of As2Se3, Ag–As2Se3, and Cu–As2Se3 chalcogenide films

Three kinds of As-chalcogenide films made of As2Se3, Ag-doped As2Se3, and Cu-doped As2Se3 were prepared using thermal evaporation and photo-doping, and their surface was illuminated in air with a focused Ar laser beam of a wavelength of 0.5145 μm. The morphology of the film surface irradiated at different optical intensities was investigated by use of optical microscopy, atomic force microscopy, and scanning electron microscopy with energy dispersive spectroscopy. It has been found that two shapes of As2O3 microcrystals are formed on the As2Se3 film at room temperature and that the formation of such microcrystals never takes place at ambient temperature over about 35 °C. Therefore the observed distribution pattern of As2O3 microcrystals is like a ring in shape for intense illumination of the focused laser beam, which indicates a spatial profile of a temperature increase caused by absorption of the laser beam. A tentative model has been presented for explaining no generation of As2O3 microcrystals above about 35 °C. It has also been confirmed that the addition of metals Cu or Ag into As2Se3 films sufficiently eliminates or weakens such a photo-oxidation reaction.