Low-temperature growth of ZnO epitaxial films by metal organic chemical vapor deposition

ZnO films were grown on Al2O3 (0001) substrates by metal organic chemical vapor deposition at temperatures of T-g = 150 similar to 300degreesC. Epitaxial growth was obtained for T-g greater than or equal to 200degreesC. The in-plane orientation of the ZnO unit cells was found to change from a no-twist one with respect to that of the substrate at T-g = 200degreesC to a 30degrees-twist one at T-g = 300degreesC. Absorption and photoluminescence were observed from the film grown at 150degreesC, although there was no evidence of epitaxial growth. Films grown at T-g less than or equal to 200degreesC exhibited smoother surfaces. Moreover, all the films grown at T-g = 150 similar to 300degreesC revealed acceptor-related emission peaks, indicating the incorporation of acceptors into the films.