Excitation-energy-dependent photoluminescence in glassy As–S and crystalline As2S3



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Photoluminescence in a chalcogenide glass system As–S and a related crystal As2S3 (orpiment) has been studied with respect to excitation spectra, temperature dependence, and sample varieties. The crystal exhibits the strongest luminescence, and in the glass system, luminescence is the most intense at the stoichiometric composition As2S3. Luminescence characteristics in the As–S glasses are substantially different under excitation of bandgap and subgap light, which seem to be governed, respectively, by spatially extended electronic relaxation and direct excitation to the gap state that produces weak absorption tails.