Photo-induced effects of the virgin Ge24.9Sb11.6S63.5 film

Amorphous Ge24.9Sb11.6S63.5 film was prepared through thermal evaporation. A blue shift of the optical band gap by approximately 100 meV was observed as a result of self-bleaching process of protected film aged for two years. The magnitude of the light induced blue shift of the optical band of the virgin film is primarily dependent on the light penetration depth and on the light intensity. The kinetics of photo-bleaching follows the stretch exponential function with a formal rate of bleaching depending on the light intensity while the saturated state is independent from the light intensity. The far infrared spectra indicate that ageing, illumination by over-band gap-photons and annealing of the virgin film are mainly accompanied by the film network ordering. Illumination by UV light photons led to a blue shift accompanied by the significant oxidation as evidenced by the results of the far infrared spectra and the energy dispersive analysis.