Preparation and properties of sol-gel ZnO thin films

Zinc oxide (ZnO) thin films were deposited on (100) silicon substrates by spin-coating using solgel synthesis and zinc acetate dihydrate was used as a starting material. The effects of different annealing atmospheres and temperatures on composition, and the structural and optical properties of ZnO thin films were investigated using Fourier transform infrared spectroscope, X-ray diffraction, atomic force microscope and photoluminescence. It was found that the ZnO thin film annealed at 400℃ in N2 ambient exhibited the optimal crystallinity and photoluminescence properties. The heat treatment at 400℃ was more suitable for the dried gel film to undergo structural relaxation, and hence more ZnO was generated in the film. The lattice constants of the ZnO samples annealed at 400℃ in N2 were obtained from XRD date (α = 0.325 3 nm, c = 0.521 nm) and a green emission around 495 nm was found in its PL spectrum due to oxygen vacancy located at the grain surface. Because ZnO grew less and the ratio of surface to volume (S/V) decreased, the green peaks decreased in intensity the increasing of the annealing temperature.