Room temperature self-assembled growth of vertically aligned columnar copper oxide nanocomposite thin films on unmatched substrates.

In this work, we report the self-assembled growth of vertically aligned columnar CuO + CuO nanocomposite thin films on glass and silicon substrates by reactive sputtering at room temperature. Microstructure analyses show that each phase in nanocomposite films has the columnar growth along the whole thickness, while each column exhibits the single phase characteristics. The local epitaxial growth behavior of CuO is thought to be responsible for such an unusual microstructure. The intermediate oxygen flow rate between those required to synthesize single phase CuO and CuO films produces some CuO nuclei, and then the local epitaxial growth provides a strong driving force to promote CuO nuclei to grow sequentially, giving rise to CuO columns along the whole thickness. Lower resistivity has been observed in such kind of nanocomposite thin films than that in single phase thin films, which may be due to the interface coupling between CuO and CuO columns.