Spectral Selectivity of Photoinduced Effects in As$_{x}$S$_{100-x}$ Glass Thin Films

Spectral dependence of photoinduced effects in As$_{x}$S$_{100-x}$ ($x=30,35,40$) amorphous thin films were studied using Raman spectroscopy, atomic force microscopy (AFM), and ellipsometry. Samples were exposed to LED light in an argon environment to avoid oxidation on the surface layer. AFM measurements reveal that our samples are of optical quality before and after exposure, allowing for application of these thin films. Ellipsometry was used measure exact penetration depths using the Beer-Lambert law. For all investigated compositions the Raman spectra taken after 375 and 405 nm exposures do not differ noticeably. The same conclusion holds for samples exposed to 450 and 525 nm light, however these two sets experienced different structural transformations. Irradiation of the virgin samples causes photopolymerization effect and significant widening of the vibrational bands. For stoichiometric comparison ($x=40$) the lower ratio between As$_{4}$S$_3$ cages and As$_{4}$S$_{4}$ units is observed for UV exposed sample in comparison with irradiated by band gap light. For all exposure wavelength there is also no evidence for S chains and S$_8$ fragments after irradiation.Theoretical calculations using density functional theory are currently underway.