TIME-RESOLVED PHOTOINDUCED ABSORPTION SPECTROSCOPIC STUDY ON TRAPPED CARRIERS AT SEMICONDUCTOR-GLASS INTERFACES

The photoinduced absorption below the band gap of a color glass filter doped by CdS0.4Se0.6 microcrystals was investigated by using time-res olved differential transmittance spectroscopy. The electron trapping a t microcrystal-glass interfaces was found to occur within less than 1 ps after photoexcitation. At low excitation energy density, the excite d electrons are trapped at point defects distributed over the nanocrys tal interfaces. Such electrons give rise to long-lived photoinduced ab sorption with a lifetime of 3.2 ns. On the other hand, at high excitat ion energy density, transient absorption with a fast (60 ps) and simul taneously a slow decay component (3.2 ns) was observed. This short-liv ed photoinduced absorption is attributed to the electrons trapped at t he shallow trap states of the semiconductor-glass interfaces.