Luminescence of excitons in mesoscopic ZnO particles

Luminescence and time-resolved luminescence spectra of ZnO particles with the size of similar to 20 nm have been investigated under band-to-band excitation. In the ultraviolet spectral region, there appear broad luminescence bands at 367.6, 368.8, 374.5 and 381.9 nm at 10 K. Decay profiles at 369 and 374 nm exhibit two decay components. The decay times are similar to 20 and similar to 100 ps for 369 nm, and similar to 40 and similar to 400 ps for 374 nm. These luminescence bands are attributable to the radiative recombination of free and bound excitons. Based on the present results, the effects of surface states and defects on excitons in mesoscopic ZnO particles have been discussed. (c) 2004 Elsevier B.V. All rights reserved.