Abstract：ZnO thin films were deposited by magnetron sputtering on SiO2 substrates. The temperature dependence of the absorption spectra and the photoluminescence spectra was studied for ZnO thin film. The absorption of the longitudinal optical (LO) phonons and the free-excitons was observed at room temperature. The free-exciton emission was only observed in PL spectra at room temperature, the results indicate that ZnO thin films have excellent quality and low density of defects. The stimulated emission properties of ZnO thin films were investigated. When excitation intensity is above threshold, the FWHM of stimulated emission peak increases and the stimulated emission peak shows red shift with increasing excitation intensity. Our analysis shows that the optical gain is due to electron-hole plasma emission.
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