Raman spectra and optical properties of thin As40S60 and As40S50Se10 films

Structure and optical properties of As40S60 and As40S50Se10 glasses and thin films have been studied using the Raman spectroscopy. The structure of the films is suggested to be basically formed by triangular AsS3 and AsSe3 pyramids linked by two-fold coordinated sulphur or selenium atoms. A considerable amount of structural units with homopolar As-As and S(Se)-S(Se) bonds has been found in the matrix of investigated compounds. The influence of illumination and annealing on the structure and optical properties of As40S60 and As40S50Se10 films has been studied. It has been shown that the mentioned actions lead to polymerization of molecular As4S(Se)4 groups and S(Se)n chains in the film matrix and formation of structural units with heteropolar As-S and As-Se bonds. This is accompanied by the absorption edge shift towards the long-wavelength region and the increase in the refractive index.