Crystallinity of NiO Nanowires Grown at Step Edges of Sapphire Substrate

Abstract

NiO nanowires were formed along atomic step edges on the ultrasmooth sapphire (0001) substrates by laser molecular beam epitaxy. From atomic force microscopy, the nanowires were found to be ∼20 nm in width and ∼0.5 nm in height along the straight, 0.2 nm-high step edges of the substrate. The crystal structure of NiO nanowires was examined by in situ coaxial impact collision ion scattering spectroscopy (CAICISS). The CAICISS results on the azimuth dependences of Ni signal for the NiO nanowires as well as NiO (111) epitaxial thin films indicate that the NiO nanowires were epitaxially grown with (111) orientation under in-plane stress.