Photoinduced changes in amorphous gallium doped GeTe4 chalcogenides

Chalcogenide thin films from the system Ge-Te-Ga were deposited by thermal vacuum evaporation on glass substrates from initial bulk synthesized materials. Optical measurements on as-deposited and irradiated thin films were performed. The optical constants - refractive index (n) and extinction coefficient (k) were evaluated from the transmission and reflectance spectra. Irradiation of the films for 3 hours through an interference filter with pass-band centered at 1,06 μm led to changes in the transmission spectra of the samples. A shift of the absorption edge was observed depending on the gallium content. The most significant change in the absorption edge was obtained in films with composition (GeTe4)95Ga5 with estimated coordination number 2.43. According to the covalent network model in glasses with coordination number close to 2.43, a floppy-rigid transition occurs. The spectral distribution of the refractive index change showed a sign inversion - from negative to positive. Changes in the physical thickness of the samples investigated due to the irradiation were not established