Magnetic properties for metastable negative-U defects in amorphous semiconductors

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• 作者：Bagraev ; Nikolai T. ; Blinov ; Lev N. ; Romanov ; Vladimir V.
• 关键词：71.23.cq ; 71.38.Mx ; 75.20.Ck ; A. Amorphous semiconductors ; D. Electron&ndash ; electron interactions ; D. Spin dynamics
• 刊名：Solid State Communications
• 出版年：2002
• 期刊代码：101_00381098
• 类别：ms
• 出版时间：March 1, 2002
• 卷：121
• 期：8
• 页码：417-421
• 文件大小：144 K

摘要

Optically induced metastable centers are studied in As₂S₃ chalcogenide glasses using the magnetic susceptibility technique for 3.5≤T≤300K. The temperature dependencies of the magnetic susceptibility (χ) exhibit spin instability of both a hole center localized at a nonbonding lone pair chalcogen orbital and an electron center formed by an As p-orbital. The χ fatigue at low temperatures is shown to result from the negative-U dissociation of paramagnetic states 2D⁰→D⁻+D⁺ that causes also the absence of an ESR signal before illumination. Irradiation with light whose energy corresponds to the Urbach tail of the absorption edge is found to result in a growing χ signal that is due to optically induced paramagnetic states revealed also by the EPR signals: D⁻+D⁺+hν→2D⁰, whereas subsequent irradiation with infrared light in the mid-gap bleaches both the optically induced magnetic susceptibility and ESR signal to its cold dark efficiency. Metastable properties for paramagnetic states located in the gap of As₂S₃ are discussed in the framework of the negative-U reaction that is accompanied by the restoration of the PL and the fatigue of the ESR signals and the magnetic susceptibility value.