Pop M. Spectrophotometric study of modified noncrystalline chalcgenides based on arsenic sulfide

The thesis is devoted to the investigation of the structure and properties of bulk glasses and amorphous films in As-S-Se and As-Sb-S systems with low content of selenium and antimony and their transformation by the chemical composition changing, heat treatment and laser irradiation. Based on the studies of Raman and Brillouin-Mandelstam light scattering spectra the microheterogeneous structure of bulk glasses of these systems has been found. The matrix of glasses built mainly by structural units AsS3/2, AsSe3/2 and SbS3/2, and contains a significant amount of structural groups with As-As, S-S, Se-Se homopolar bonds. Optical absorption spectra of bulk glasses and As-S-Se, As-Sb-S amorphous films were investigated, also calculated their optical parameters. It is shown that in the investigated materials the shape of exponential absorption edge is determined by the electron-phonon interaction and its energy position, width is defined by the influence of different types of disordering. The irradiation and annealing effects on the optical properties of amorphous films As40S60-xSex and As40-ySbyS60 have been investigated. It is shown that their action leads to the polymerization of molecular groups with homopolar bonds participating in the formation of the film matrix, which accompanied by shifting of the absorption edge in the long-wavelength range. The role in this process of structural defects of over- and uncoordinated As(Sb) and S(Se) atoms was established. Based on these studies were revealed the most photosensitive materials that can be used as recording media for optical recording media.