Diffusion-controlled electrochemical growth of porous zinc oxide on microstructured electrode band arrays

Films of zinc oxide were prepared by electrochemical deposition at constant electrode potential from an oxygen-saturated aqueous zinc-chloride solution on rotating microband electrode arrays of gold or silver on SiO2/Si wafers. Porous ZnO films were obtained by deposition in the presence of the xanthene dye eosinY as a structure-directing agent. The electrode size, the gap width, the number of electrode bands, the deposition time, and the rotation rate were varied. The growth of ZnO was monitored by the observed current, and the films were subsequently characterized by profilometry and by scanning electron and confocal laser microscopy. Strongly enhanced growth was observed at the edges of the electrode bands. This was explained by models of hemi-cylindrical diffusion revealing inhomogeneous mass transport to the electrodes. The models were extended to processes of electrochemical deposition. A model for diffusion-limited growth on microstructured electrode band arrays is proposed and applied to the present results.