ZnO Thin Films Prepared by Electrochemical Deposition Method at Constant Current Density
Atsushi ASHIDA and Norifumi FUJIMURA
Abstract:ZnO thin films were prepared from an aqueous zinc nitrate solution by an electrochemical deposition method. To control the growth rate of the ZnO films, electrochemical deposition was carried out by applying constant current density, rather than constant potential as in conventional methods. The preferred orientation of ZnO films deposited on polycrystalline Au electrodes changed depending on the cathodic current density. The grain size and grain shape could also be controlled by changing the current density. An epitaxial layer of Pt(111) on c-sapphire was also used as an electrode. ZnO films prepared by application of high current densities exhibited not only (0002) orientation but also other orientations. At low current densities, the deposition formed not a film but rather isolated hexagonal columnar grains on the electrode. At intermediate cathodic current densities, epitaxial ZnO thin films were obtained. At 100 ƒÊA/cm2, a continuous epitaxial ZnO thin film without pits or spaces between grains was obtained. Therefore, it is expected that the proposed electrochemical deposition method has potential to be applied to preparation of functional materials with well-controlled structures. Key Words:Electrochemical deposition, Zinc oxide, Cathodic current, Epitaxial growth, Grain size