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 degrees. The ZnO(0001) plane of the wires aligned with Al2O3(10 (1) over bar4) 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) over bar0] in two preferred in-plane orientations, 72 degrees-74 degrees apart. These configurations could be explained by two distinct alignments of the ZnO(10 (1) over bar1) plane on the a-plane sapphire substrate surface, promoted by low lattice mismatches. (C) 2012 Elsevier B.V. All rights reserved.