Photoluminescence studies of ZnO thin films prepared using a laser-assisted sol-gel method

ZnO thin films were grown on Si(100) substrates by using a laser-assisted sol-gel method involving irradiation from a 325-nm He-Cd laser. In contrast to conventionally-synthesized sol-gel ZnO thin films, the surfaces of those grown using the laser-assisted sol-gel method were much smoother. The optical properties of the ZnO thin films were investigated using temperature-dependent photoluminescence (PL). In the room-temperature PL spectra, the intensity of the blue-green emission was dramatically decreased by laser irradiation during the stages of deposition and post-heat treatment. Moreover, the full width at half maximum of the near-band-edge emission peaks was decreased by the laser irradiation. The activation energy of the laser-assisted sol-gel ZnO thin films was determined to be similar to 99 meV, and the values of the fitting parameters alpha and beta for Varshni's empirical equation were 4 x 10(-3) eV/K and 4.9 x 10(3) K, respectively. Another fitting based on the thermal broadening effect of the excitonic emission peak revealed a decreased exciton-phonon interaction in the laser-assisted ZnO thin films.