Transient absorption study on photodarkened CdSxSe1-x doped glasses: Evidence for long lived trapping states

We present here the results of transient absorption spectroscopy on photodarkened nanocrystalline CdSxSe1-x doped glasses. The observed transient absorption decayed with time constants of few tens of microseconds, indicating that long lived trapping states are present in the photodarkened CdSxSe1-x, doped glasses. The transient absorption spectra changed with the size of the CdSxSe1-x particle. The intensity of the transient absorption was higher in the sample with smaller particle size than in the sample with larger size. This suggests that the increase in the surface/volume ratio in the CdSxSe1-x particle is somehow related to the increase of the transient absorption intensity. The pump-energy dependence of the lifetime of the trapping state and a tentative interpretation for the dependence are given. No vibrational features in the trapping states were found in the phonon Raman spectra.