Nanoscale mechanism of photoinduced metastability and reversible photodarkening in chalcogenide vitreous semiconductors

The present paper reviews the results oblained by the authors in the last three years. By applying in-situ (pamp and probe) EXAFS to reversible photostructural changes in chalcogenide vitreous semiconductors we have found an increase in the average coordination number of selenium species in the photoexcited state which comes from the formation of dynamic interchain bonds. Subsequent bond rupture, studied by optically induced ESR, results in the formation of over-and undercoordinated ESR-active defects, which are further transformed into charged valence-alternation pairs. Annealing close to the glass-transition temperature results in recovery of the initial structure. Relationship between the detected structural changes and photodarkening is also discussed.

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