Raman evidence for the oxidation of amorphous As₂(Se_xS_1–x)₃ film surfaces under visible light

Abstract

Raman spectra of thermally evaporated As2Se3 and Se-rich (above 50 at. %) ternary As–Se–S films measured at high (above 1 MW/cm2) excitation power density reveal new narrow peaks emerging during the measurements which are attributed to crystalline arsenolite As2O3. The latter is formed on the As–Se–S film surface due to thermal decomposition of the film and oxidation of arsenic in ambient air. Contrary to As2S3, for which the photoassisted oxidation of the film surface requires UV light, for narrower-gap As–Se–S films this effect occurs under illumination by visible light.