EPITAXIAL ALUMINUM-DOPED ZINC-OXIDE THIN-FILMS ON SAPPHIRE .1. EFFECTOF SUBSTRATE ORIENTATION

Epitaxial thin films of Al-doped zinc oxide have been grown on sapphir e substrates by pulsed laser ablation, The effect of substrate tempera ture, background pressure of oxygen, and substrate orientation (A, M, R, C) on the orientation relationships between ZnO and sapphire have b een evaluated using on- and off-axis X-ray diffractometry, Under all g rowth conditions zinc oxide, on A- and C-plane sapphire, grew with the c-axis perpendicular to the substrate, In contrast, on M and R orient ations of sapphire, ZnO grew with its c-axis parallel or perpendicular to the substrate depending on the substrate temperature and backgroun d pressure employed during growth. In all cases only one unique in-pla ne relationship between the sapphire substrate and the zinc oxide film was found with the exception of the M-plane at high substrate tempera tures.