Modulating ZnO Nanostructure Arrays on Any Substrates by Nanolevel Structure Control

Abstract

A uniform high-aspect-ratio nanotextured surface with a very dense forest of vertically aligned nanowires that was produced by surface chemical postfabrication of ZnO was induced by a structural transformation at the nanolevel. X-ray photoelectron spectroscopy verified the formation of the heterogeneous surface structures (GaO(x) on GaN and AuO(x) on Au) at the nanolevel as well as the modification of surface stoichiometry by UV/ozone treatment. The structural transformation contributes to generating a surface charge, acting as nucleation sites for nanotip growth. This led to a significant increase in density and improvement in diameter of the nanotips for various substrates, such as ZnO, Au, GaN, and graphene. However, the surface oxygen by O(2), plasma treatment reduced the activity as activation sites of the exposed surface, resulting in the decrease of the density of the nanotips. This rational engineering of substrates by a structural transformation at the nanolevel may provide a promising method for producing highly dense one-dimensional nanomaterials.