Observation of enhanced bleaching and fast recovery in CdS/sub 0.4/Se/sub 0.6/ nanocrystals

Semiconductor nanocrystals have been a subject of increasing interest due to various unique physical properties. Besides the quantum confinement in all three dimensions, various trapping processes are important factors to understand the ultrafast carrier dynamics in nanocrystals. The trapping into the surface states has been suggested to be a possible deactivation channel for the fast carrier relaxation in band-edge photoluminescence. Moreover, it is reported that photodarkening due to two photon absorption has been observed by trapping electrons into the glass electronic states. In our experiment, femtosecond transient absorption of CdS/sub 0.4/Se/sub 0.6/ nanocrystals in a glass matrix (Schott Glass RG630) has been measured to study the trapping effect on the bleaching dynamics.