Finger prints of chemical bonds in Sb–Se–Ge and Sb–Se–Ge–In glasses: A Far-IR study

Chalcogenide glasses exhibit good optical properties because of their ability to transmit in the infrared region. Far-Infrared transmission spectra give an insight into the absorbed frequencies of the light corresponding to the characteristic vibration of the isolated molecular units. Ge and In have been used as additives in Sb10Se90 and Sb10Se65Ge25 alloys, respectively. The role of Ge on the formation of a 3-dimensional network, through the apparition of GeSe4 and GeSe2 units at the expense of SbSe3 and Se8 groups, is evidenced, due a higher tendency of Ge to spontaneously form linkages with the other elements of the medium. When Ge is substituted by In, the glass rearranges due to the progressive disappearance of GeSe2 and GeSe4 units. SbSe3 and Se8 reappear accompanied by InSe4 and In–In units. These results are comforted by the calculation of the bond probabilities and vibration frequencies.