Zinc oxide films were prepared on Si(111) substrates by sol-gel spin-coating technique.Structure,photoluminescence,and surface morphology of ZnO thin films processed at various temperatures and times were investigated.Results showed that ZnO thin films showed a hexagonal wurtzite structure,and the extent of c-axis orientation was dependent on the processing temperature.All the thin films emitted strong band to band UV emission without defects related visible emissions at room temperature when the processing temperature was below 550℃.When the processing temperature exceeded 550℃,a strong emission band appeared in the visible region.Results also showed that the photoluminescence spectrum was dependent not only on the processing temperature but also on the processing time.Long time(3 hours) processing resulted in the aggregation of ZnO grains in the film and a lower band to band emission in the photoluminescence spectrum.