PHOTODARKENING ENERGY-STATE IN NANOCRYSTALLINE CDSXSE1-X-DOPED GLASS PROBED BY TIME-RESOLVED RAMAN-SPECTROSCOPY

We studied the photodarkening effect in nanocrystalline CdSzSe1-x-dope d glasses by pump-probe time-resolved Raman spectroscopy. A marked dec rease in the phonon Raman intensities was observed when the photodarke ned samples (commercial glass color filters) were pre-excited by the p ump pulse. Such an intensity change was not observed for the fresh (un photodarkened) samples. These findings have been interpreted in terms of a new photodarkening-induced state that traps the photoexcited elec trons efficiently. The magnitude of the decrease in Raman intensities increased linearly with increasing selenium fraction, suggesting that the photodarkening energy state is related to the Se anion or correspo nding vacancy on the surface of CdSxSe1-x microcrystallites.