Micromechanism and kinetic formulation of vertically aligned ZnO nanorods grown on catalytic bilayers

Abstract

Vertically aligned ZnO nanorods were grown at 700°C for 2 h on sapphire substrates with catalysts in bilayer configurations of Sn (top)/Ni (bottom) and Sn/In, where the top layer is formed by sputtering and the bottom one is deposited by spin coating. The effects of bilayer catalysts on growth kinetics of nucleation and growth, growth micromechanism, and vertical alignment of growing ZnO nanorods have been investigated. The vertical alignment of the Sn/Ni-catalyzing ZnO nanorods is determined at the initial nucleation stage, where the nuclei are formed as regular candlestick-like platforms. The reason for the formation of the candlestick-like nuclei is due to the contribution of strain energy built in the underlying catalyst bilayers. The variations of axial and radial dimensions with growth duration for the growth of ZnO rods were explained and data fitting with the aids of kinetic growth equations, which are based upon the well-known ledge model for crystal growth from vapor and diffusion kinetics. © 2012 Dong-Hau Kuo and Jheng-Yu He.