Correlation between grain size and optical properties in zinc oxide thin films

Photoluminescence (PL) and time-resolved PL spectra of zinc oxide (ZnO) films were investigated as a function of the grain size of the microcrystals. Correlation was found between the grain size and the optical properties—in the bound exciton states, both the PL intensity and PL decay time increased with increasing the grain size. This correlation can be well explained by the existence of nonradiative-surface and/or -interface states in the grain boundaries of ZnO microcrystals.