| Popis: |
The atomic structure of ${\mathrm{Si}}_{x}{\mathrm{S}}_{1\ensuremath{-}x}$ glasses is investigated by the use of Raman spectroscopy. The compositional dependence of the microstructures of these glasses can be conveniently divided into three regions. At Si${\mathrm{S}}_{2}$, the glassy structure is composed of randomly oriented edge-sharing $\mathrm{Si}{({\mathrm{S}}_{\frac{1}{2}})}_{4}$ tetrahedral chains. Excess Si ($xg\frac{1}{3}$) is accomodated in the glasses as ethanelike ${\mathrm{S}}_{3}$-Si-Si-${\mathrm{S}}_{3}$ units. For Si-poor glasses, an unusual compositional dependence is observed of the Raman mode associated with the extended Si${\mathrm{S}}_{2}$ edge-sharing tetrahedral chains. This behavior is related to the emergence of isolated $\mathrm{Si}{({\mathrm{S}}_{\frac{1}{2}})}_{4}$ tetrahedral units as the Si content of the glasses is decreased below $x=0.25$. In the Si-poor glasses, ${\mathrm{S}}_{8}$ units, fragments of ${\mathrm{S}}_{8}$ units, isolated ${\mathrm{S}\mathrm{i}({\mathrm{S}}_{1/2})}_{4}$ tetrahedral units, and Si${\mathrm{S}}_{2}$ units are observed. The present work is the first to address the question of the microstructure of chalcogenide-rich Si glasses. |
