Spontaneous ZnO nanowire formation during oxidation of Cu-Zn alloy

A combination of electron microscopy and in-situ x-ray diffraction is employed to study the thermal oxidation of brass (Cu_0.7Zn _0.3 alloy) in order to elucidate the mechanism of one-dimensional growth of ZnO nanostructures. Oxidation of the brass alloy results in the growth of a ZnO overlayer with ZnO nanowire formation on the ZnO layer. Increasing the oxidation temperature thickens the ZnO overlayer while suppressing ZnO nanowire formation on the top, which provides clear evidence that the formation of ZnO nanowires is related to a stress-driven mechanism that involves accumulation of compressive stress generated from the ZnO/Cu-Zn interfacial reaction and relaxation of the compressive stress by outward grain-boundary diffusion of Zn.