GexSb20Se80-x玻璃的拉曼光谱和X射线光电子能谱

用拉曼散射光谱和X射线光电子能谱研究了Ge_xSb₂₀Se_80-x(x=5 mol%, 10 mol%, 15 mol%, 17.5 mol%, 20 mol%和25 mol%)玻璃的结构. 通过对拉曼光谱和X射线光电子能谱(Ge 3d, Sb 4d 和Se 3d谱)进行分解, 发现当硫系玻璃处于富Se状态下时, 玻璃结构中会出现Se–Se–Se结构单元, 其数量随着Ge含量的增加而迅速减少, 并最终在Ge₁₅Sb₂₀Se₆₅玻璃结构中消失; Ge和Sb原子分别以GeSe_4/2 四面体和SbSe_3/2三角锥结构单元在玻璃结构中出现, GeSe_4/2四面体结构单元的数量会随着Ge浓度的增加而增加, 而SbSe_3/2三角锥结构单元的数量基本保持稳定. 另一方面, 在缺Se的硫系玻璃中, 玻璃会有Ge–Ge和Sb–Sb同极键产生, 随着Ge含量的增大, 这种同极键的数量会越来越多; 而GeSe_4/2四面体和SbSe_3/2三角锥结构的数量则相应减少. 在所有玻璃样品的结构中均有同极键Se–Se的存在. 当玻璃组分越接近完全化学计量配比时, 异质键Ge–Se和Sb–Se将占据玻璃结构中的主导地位, 同极键Ge–Ge, Sb–Sb和Se–Se 的比例降为最小.

Raman scattering and X-ray photoelectron spectra of GexSb20Se80-x Glasses

In this paper, we prepare several Ge_xSb₂₀Se_80-x glasses (x=5 mol%, 10 mol%, 15 mol%, 17.5 mol%, 20 mol%, and 25 mol%), and measure their Raman and X-ray photoelectron spectra (Ge 3d, Sb 4d, and Se 3d) in order to understand the evolution of the glass structure with chemical composition. We further decompose the spectra into different structural units according to the assignments of these structural units in the previous literature. It is found that the structural units of Se–Se–Se trimers exist in the Se-rich glasses, but the number of the structural units of trimers decreases rapidly with the increase of Ge concentration and finally becomes zero in Ge₁₅Sb₂₀Se₆₅ glass. With the increase of Ge concentration, the quantity of GeSe_4/2 tetrahedral structures increases, but the number of SbSe_3/2 pyramidal structures remains almost unchanged in the Se-rich glasses. On the other hand, the numbers of Ge–Ge and Sb–Sb homopolar bonds increase with the increase of Ge concentration, but those of the GeSe_4/2 tetrahedral and SbSe_3/2 pyramidal structures decrease in the Se-poor glasses. Moreover, the Se–Se homopolar bonds exist in all the glasses, and they cannot be completely suppressed. When the composition is close to stochiometric value, the glass is dominated by heteropolar Ge–Se and Sb–Se bonds, but has negligible quantities of Ge–Ge, Sb–Sb and Se–Se homopolar bonds. The transition threshold, rather than the transition predicted by the topological constraint model, occurs at the chemically stoichiometric glasses. This suggests that chemical order, rather than topological order, is a main factor in determining structures and physical properties of Ge–Sb–Se glasses.