(SixGe1−x)S2glasses: Networks of separate molecular clusters

Abstract

The question of isoelectronic substitution in chalcogenide glasses is explored. Raman measurements on $\left({\mathrm{Si}}_x{\mathrm{Ge}}_{1-x}\right)$ ${\mathrm{S}}_2$ glasses reveal a microstructure consisting of separate Si${\mathrm{S}}_2$ and Ge${\mathrm{S}}_2$ molecular clusters. The short- and medium-range order of these clusters appears to be unperturbed by alloying. The present results provide strong evidence for the existence of molecular clusters in glasses and illustrate a connection between intramolecular forces and medium-range order of the clusters. The differences between the Si${\mathrm{S}}_2$ and Ge${\mathrm{S}}_2$ clusters are discussed in relation to differences between the corresponding crystalline compounds.