Nanosecond dynamics of photodarkening in amorphous chalcogenide

We have performed precise measurements of the transient optical absorption spectra of amorphous (a-) As2Se3 and As2S3 at room temperature in the nanosecond and microsecond domains. From the measurements, we have observed the photodarkening in the nanosecond and microsecond domains for both of the samples. For a-As2Se3, a broad absorption peak in the range from 420 to 730 nm was observed. The peak maximum changed to longer wavelength with time. For a-As2S3, a sharp absorption peak in the range from 420 to 510 nm and a long absorption tail in the range from 510 to 600 nm were observed. The peak maximum does not change with time. Based on the experimental results, we discuss the nanosecond dynamics of the photodarkening in terms of the local structural changes.