Lifetimes of excitons in ZnO fine particles dispersed in alkali halide crystals

We have investigated time-resolved luminescence spectra of excitons in ZnO raw powders of micrometer size and those particles dispersed in a thin KI crystal under the band-to-band excitation of ZnO. The decay times of the bound excitons have been examined in both the samples. The bound exciton luminescence line in ZnO particles dispersed in KI crystal shows two decay components, much shorter than the decay time (165±3 ps) of the bound exciton line observed in the raw powders, and has the spectral shape with a long tail toward the longer-wavelength side. On the basis of the present results, we discuss the interface effects on the excitonic states in the ZnO fine particles dispersed in KI crystal.