Preparation of ZnO thin films on sapphire substrates by sol-gel method

ZnO films have been prepared on (0001) sapphire substrates by the sol-gel method from a 2-methoxyethanol solution of zinc acetate dihydrate stabilized by monoethanolamine. The structural properties of the films have been characterized by X-ray diffraction, compared with the films on silica glass substrates. The crystallinity was enhanced in the ZnO films on sapphire substrates by increasing heat-treatment temperature, whereas it was degraded in the films on silica glass substrates at heat-treatment temperatures above 700degreesC. Completely (0001)-oriented ZnO films were successfully prepared by heat-treatment at temperatures above 800degreesC on (0001) sapphire substrates annealed at 1000degreesC in air. The c-axis lattice constants of the ZnO films on sapphire substrates were larger than those of bulk ZnO and ZnO films on silica glass substrates.