Selective growth and kinetic study of copper oxide nanowires from patterned thin-film multilayer structures

Selective growth of CuO nanowires on the etched face of Al₂O₃/Cu/Al₂O₃ thin-film multilayer patterns was achieved by ambient oxidation at 400 °C. The nanowires were observed to selectively grow only from the pattern edge with diameter limited by the thickness of Cu thin film. Transmission-electron-microscopy (TEM) characterization confirmed CuO nanowires of a monoclinic CuO growing in the [010] crystallographic direction. Nanowire growth kinetics was studied at 400 °C for different cumulative growth durations with initial growth rates of ∼1 nm/min. A base growth mechanism with kinetics limited by oxygen diffusion through defects of a scaling oxide film is consistent with observed kinetics. The oxygen diffusivity is found to be ∼10⁻¹¹ cm²/s, consistent with the grain-boundary diffusion of oxygen through polycrystalline copper oxide.