Epitaxial relationships of ZnO nanostructures grown by Au-assisted pulsed laser deposition on c- and a-plane sapphire

Abstract We report on the epitaxial growth of ZnO nanosheets and nanowires on a - and c -plane sapphire substrates by Au-assisted pulsed laser deposition. The epitaxial relationship of the nanostructures was determined by x-ray diffraction (XRD) pole figure measurements. On c -plane sapphire, the ZnO nanowires grew along the ZnO c -axis and were inclined to the substrate surface normal with an angle of about 37°. The ZnO(0001) plane of the wires aligned with Al 2 O 3 ( 10 1 ¯ 4 ) of the sapphire substrate via two degenerate in-plane configurations, promoted by low lattice mismatch (0.05%). ZnO nanosheets grown on c -plane sapphire exhibited no preferential orientation on the substrate and no epitaxial relationship could be unambiguously identified. On a -plane sapphire, ZnO nanowires grew vertically along the ZnO c -axis with a single epitaxial configuration, whereas ZnO nanosheets seemed to grow along ZnO [ 10 1 ¯ 0 ] in two preferred in-plane orientations, 72°–74° apart. These configurations could be explained by two distinct alignments of the ZnO ( 10 1 ¯ 1 ) plane on the a -plane sapphire substrate surface, promoted by low lattice mismatches.