Mechanism of photostructural changes in mixed-chalcogen As–S–Se glasses investigated by Raman spectroscopy

• Published in: Journal of physics. D, Applied physics Vol. 44; no. 4; p. 045404
• Main Authors: Lin, Fang-Yin, Gulbiten, Ozgur, Yang, Zhiyong, Calvez, Laurent, Lucas, Pierre
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 02.02.2011; Institute of Physics
• Subjects: Band spectra; Banded structure; Bands; Chemical Sciences; Condensed matter: structure, mechanical and thermal properties; Decay; Disordered solids; Exact sciences and technology; Glass; Glasses; Material chemistry; Oscillators; Photosensitivity; Photostructural changes; Physics; Structure of solids and liquids; crystallography; Arsenic Selenides sulfides; Line intensity; Photosensitivity; Raman spectra; Illumination; Structure modification; Chemical composition; Glass structure; Chalcogenide glasses
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/44/4/045404

The structure and photosensitivity of chalcogen-rich As–S–Se glasses are investigated ex situ and in situ. The Raman spectra of these glasses exhibit three well-defined bands associated with Se-based, S-based and mixed Se–S based structural units. The deconvolutions of these bands show a coherent correlation between intensity and composition. It is then shown that the magnitude of photoexpansion and photorefraction measured ex situ increases continuously with Se content therefore indicating a central role of Se atoms in the mechanism of photostructural changes. The key role of Se is indeed directly observed and confirmed using in situ Raman characterization. It is shown that the band associated with Se–Se oscillators decays continuously during photostructural changes. Furthermore, it is shown that the kinetics of Raman decay closely matches the kinetics of photoexpansion when measured simultaneously. Overall these results demonstrate the central contribution of Se–Se fragment during sub-bandgap irradiation which is consistent with the presence of Se lone pair states at the top of the valence band.