New type of charged defect in amorphous chalcogenides

We report on density-functional-based tight-binding simulations of a series of amorphous arsenic sulfide models. In addition to the charged coordination defects previously proposed to exist in chalcogenide glasses, a novel defect pair, [As(4)](-)-[S(3)](+), consisting of a fourfold coordinated arsen...

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Bibliographic Details
Published in:Physical review letters 2005-03, Vol.94 (8), p.086401.1-086401.4, Article 086401
Main Authors: SIMDYANKIN, S. I, NIEHAUS, T. A, NATARAJAN, G, FRAUENHEIM, Th, ELLIOTT, S. R
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Disordered structures
amorphous and glassy solids
Electron states
Exact sciences and technology
Impurity and defect levels
Physics
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Summary:We report on density-functional-based tight-binding simulations of a series of amorphous arsenic sulfide models. In addition to the charged coordination defects previously proposed to exist in chalcogenide glasses, a novel defect pair, [As(4)](-)-[S(3)](+), consisting of a fourfold coordinated arsenic site in a seesaw configuration and a threefold coordinated sulfur site in a near-planar trigonal configuration, was found in several models. The valence-alternation pairs [S(3)](+)-S-1 are converted into [As(4)](-)-[S(3)](+) pairs under HOMO-to-LUMO electronic excitation. This structural transformation is accompanied by a decrease in the size of the HOMO-LUMO band gap, which suggests that such transformations could contribute to photodarkening in these materials.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.94.086401