Li Wang
Beijing University of Technology, China
Title: Photoelectron spectra of GexSb20Se80-x Glasses
Biography
Biography: Li Wang
Abstract
Several GexSb20Se80-x glasses are prepared (x=5, 10, 15, 17.5, 20 and 25 mol%), and measured their Raman and X-ray photoelectron spectra (Ge 3d, Sb 4d and Se 3d) in order to understand the evolution of the glass structure as a function of chemical composition. We further decomposed the spectra into different structural units following the assignments of these structural units in the previous literature. It was found that, Se-Se-Se trimers structural units exists in the Se-rich glasses, but the number of the trimers structural units decreases rapidly with increasing Ge concentration and finally becomes zero in Ge15Sb20Se65 glass. With increasing Ge concentration, the amount of GeSe4/2 tetrahedral structure increases and that of SbSe3/2 pyramidal structure remains almost no changes in the Se-rich glasses. On the other hand, the number of Ge-Ge and Sb-Sb homopolar bonds increases with increasing Ge concentration, and that of the GeSe4/2 tetrahedral and SbSe3/2 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 chemical stoichiometry, the glass is dominated by heteropolar Ge-Se and Sb-Se bonds with negligible amount of Ge-Ge, Sb-Sb and Se-Se homopolar bonds. The transition threshold occurred at the chemically stoichiometric glasses rather than the transition predicted by the topological constraint model suggested that, chemical order rather than topological order is a main factor in determining structure and physical properties of Ge-Sb-Se glasses.
