ZnO Morphology Control by Pulsed Electrodeposition

ZnO films have been grown by pulsed electrochemical deposition between a reduction potential and an oxidation potential to improve their quality. Different morphologies like columns, platelets, flowers, and high-quality planar films are obtained changing the reduction potential without further addition of additives. The mechanism behind this control in morphology is ascribed to the OH − concentration at the electrode surface (pH) as a consequence of the reduction potential. The morphology, surface potential, and electrical conduction mechanism of high-quality ZnO films were simultaneously measured by kelvin probe force microscopy (KPFM). As a result of these measurements, one can conclude that the ZnO surface perpendicular to the (0001) direction is positively charged. Also, it becomes evident that the surface potential drop is mainly produced at the grain boundaries for the ZnO films grown by pulsing between −0.5 and 0.9 V, which indicates intergrain contact resistance.