Structural evolution study of additions of Sb_2S_3 and CdS into GeS_2 chalcogenide glass by Raman spectroscopy

The structures of pseudo-binary GeS₂-Sb₂S₃, GeS₂-CdS, Sb₂S₃-CdS, and pseudo-ternary GeS₂-Sb₂S₃-CdS chalcogenide systems are systematically investigated by Raman spectroscopy. It is shown that a small number of[S₃Ge-GeS₃] structural units (SUs) and -S-S-/S₈ groups exist simultaneously in GeS₂ glass which has a three-dimensional continuous network backbone consisting of cross-linked corner-sharing and edge-sharing[GeS₄] tetrahedra. When Sb₂S₃ is added into GeS₂ glass, the network backbone becomes interconnected[GeS₄] tetrahedra and[SbS₃] pyramids. Moreover, Ge atoms in[S₃Ge-GeS₃] SUs tend to capture S atoms from Sb₂S₃, leading to the formation of[S₂Sb-SbS₂] SUs. When CdS is added into GeS₂ glass,[Cd₄GeS₆] polyhedra are formed, resulting in a strong crystallization tendency. In addition, Ge atoms in[S₃Ge-GeS₃] SUs tend to capture S atoms from CdS, resulting in the dissolution of Ge-Ge bond. Co-melting of Sb₂S₃ or CdS with GeS₂ reduces the viscosity of the melt and improves the homogeneity of the glass. The GeS₂ glass can only dissolve up to 10-mol% CdS without crystallization. In comparison, GeS₂-Sb₂S₃ glasses can dissolve up to 20-mol% CdS, implying that Sb₂S₃ could delay the construction of[Cd₄GeS₆] polyhedron and increase the dissolving amount of CdS in the glass.