Synthesis, structure and optical properties of thin films from GeS2-In2S3 system deposited by thermal co-evaporation

This paper deals with the properties of the glasses and thin films from multi-component chalcogenide prepared by co-evaporation technique. The thin chalcogenide layers from GeS2-In2S3 system were deposited by thermal co-evaporation of GeS2 and In2S3. Using X-ray microanalysis it was found that the film compositions are closed to the expected ones. X-ray diffraction analysis shows that the thin films deposited by co-evaporation are amorphous. The refractive index, n and the optical band gap, Eoptg were calculated from the transmittance and reflectance spectra. The thin film's structure was investigated by infrared spectroscopy. It was found that the photo-induced optical changes decrease with increase of indium content while significant thermo-induced changes in the optical properties and structure were observed at 14 at.% indium. The infrared spectra demonstrated high transmittance of the thin films in the range 4000-500 cm-1. The far-infrared spectra indicated that the indium participates in the glass network of the layers from Ge-s-In system in four coordinated InS-4/2 tetrahedral and six-coordinated InS3-6/2 octahedral units. The changes in infrared spectra after annealing of the thin films evidence an increase of population of ethane-like S3Ge-GeS3 units and/or structural or phase change of indium contain units.