Photo- and thermally induced changes in the refractive index and film thickness of amorphous As2S8 film.

Changes in the refractive index and thickness of amorphous As2S8 semiconductor film are observed under illumination, annealing–illumination, and annealing-illumination cycles. Properties of the As2S8 film are measured using techniques of prism coupler, x-ray diffraction spectra and Raman spectra. After light illumination the refractive index change in an as-deposited As2S8 film is one order of magnitude greater than that of an annealed As2S8 film, corresponding to ∼0.06 and ∼0.0057, respectively. Photoexpansions with a change in the relative film thickness of the as-deposited and annealed As2S8 film are nearly -3.5% and -2.1%, respectively, which exhibit the photodensification. The full reversibility of the photoinduced refractive index change is claimed on an annealed As2S8 film sample. [ABSTRACT FROM AUTHOR]