Optical properties of nanosized ZnO films prepared by sol-gel process

Nanosized ZnO films were prepared by sol-gel process on quartz substrates. The effects of sol concentration and annealing temperature on the surface morphology, microstructure and optical properties of the films were investigated. The results show that the sols remain stable and usable for spin-coating within 7 d. The ZnO films have a homogeneous and dense surface with grain size about 30 nm. The ZnO thin film annealed at 500 degrees C for 1 It from the sol with Zn concentration of 0.8 mol/L shows an average transmittance of 94% in visible wavelength range. The optical band gaps in ZnO films by various annealing temperatures are from 3.265 eV to 3.293 eV. The violet emission located at 438 nm is probably due to the recombination transitions relating to the interface traps at the grain boundaries.