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

Abstract

In this work, we report the self-assembled growth of vertically aligned columnar Cu₂O + Cu₄O₃ 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 Cu₂O is thought to be responsible for such an unusual microstructure. The intermediate oxygen flow rate between those required to synthesize single phase Cu₂O and Cu₄O₃ films produces some Cu₂O nuclei, and then the local epitaxial growth provides a strong driving force to promote Cu₂O nuclei to grow sequentially, giving rise to Cu₂O 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 Cu₂O and Cu₄O₃ columns.