Fabrication of Cu/Cu2O composite nanowire arrays on Si via AAO template-mediated electrodeposition

Cu/Cu2O composite nanowire arrays on Si substrate with an Au interlayer have been prepared by anodic aluminum oxide (AAO) template-mediated electrochemical deposition. The pure Cu2O nanowires are obtained at low current density, 0.05 mA/cm2, while pure Cu nanowires appear at high current density, 15 mA/cm2. Between these two current densities, the Cu/Cu2O composite nanowires are produced and the content of Cu increase as the applied current density is raised. The transmission electron microscopy (TEM) observation indicates that the composite nanowires are composed of isolated Cu and Cu2O grains, which contradicts to the layered structure observed in the composite films. The spontaneous potential oscillation observed in preparing Cu/Cu2O composite films is also recorded during the formation of composite nanowires. The periods of spontaneous oscillation are a function of the applied current density. The mechanism of the variation of local pH can account the occurrence of spontaneous potential oscillations in the present system.