Compositional variation in the structure of Ge–S glasses

X-ray photoelectron spectroscopy (XPS), and X-ray fluorescence (XRF) and Raman spectroscopies have been used to characterize the structure of Ge–S binary glasses in the compositional range 57–90 at.% S, together with evaluating the valences of Ge and S. XPS reveals that Ge4+ and Ge2+ states are formed and especially, Ge2+ exists in the range 57–62 at.% S. The roles of Ge4+- and Ge2+-relating species in glass structure are discussed. The combined results of XRF and Raman spectroscopies suggest that S–S bonds are present in all the S-rich glasses of >67 at.% S, short S chains are formed up to 76.5 at.% S and then S8 rings are formed at the S-richer side. The compositional dependence of the molar volume calculated from the measured densities of glasses is qualitatively related to the structural units of the Ge–S glasses.