Abstract
The 3.33 eV photoluminescence line is investigated in ZnO thin films deposited by dip coating. These films are oriented along the c-axis and exhibit basal-plane stacking faults and random grain boundaries. It is found that the relative intensity of the free exciton peak to the 3.33 eV line decreases as the nanoparticle size is reduced and that the corresponding Huang–Rhys factor is about 0.5. This reveals that excitons bound to extended defects at grain boundaries are involved. Also, post growth annealing strongly affects the photoluminescence spectra. In particular, the 3.31 eV line coming from stacking faults is enhanced at high annealing temperature.