Growth of ZnO nanowires using thermal oxidation process

Abstract

Controlled thermal oxidation of thin zinc (Zn) films grown on glass substrate has been performed in an air ambient condition to achieve extremely long and uniform high quality ZnO nanowires. High purity Zn layers were thermally evaporated on ex situ chemically cleaned glass slides at room temperature using a vacuum coater unit under a base pressure < 10-5 mbar. Structural characterization and morphology studies of these thermally oxidized ZnO films using XRD and FESEM techniques. The chemical and optical properties of the ZnO nanostructures have also been tested using a Raman spectroscopy. All findings are complementary to each other and suggest that the oxidation starts at about 400 °C with a severe surface roughening of the Zn film. For lower oxidation temperature (<500 °C) lateral growth of ZnO film is preferred whereas at higher oxidation temperature (above 600 °C) asymmetric growth starts to dominates which finally leads to the formation of ZnO nano-wires of a very high aspect ratio of 1000.