A Model for the Anodic Dissolution of the Zinc Electrode in the Prepassive Region

Yu-Chi Chang
1989 Journal of the Electrochemical Society  
In two previous publications (1, 2) it has been shown that thermal oxidation of liquid indium metal droplets gives rise to hollow, hemispherical In203 structures which exhibit maximum quantum efficiencies of 290% at 310 nm. Oxide films of the same mean thickness, grown in essentially the same way except that they were exposed to the oxygen plasma during oxidation gave maximum quantum efficiencies of =40%; these films being referred to as plasma oxidized In203. On the other hand, uniform, flat
more » ... nd, uniform, flat films of In20~ grown by reactive sputter deposition from an indium metal target in a 100% 02 plasma, exhibited maximum quantum efficiencies of =18% at 290 nm. The source of the vast improvement of the rough thermally grown films over the flat sputter-deposited films was shown to be comprised of two contributions, one based on geometry and the other related to an improvement in the solid-state properties of the former over the latter. While the plasma oxidized films have the same geometry as the thermally grown films, they were exposed to the oxygen plasma for =2 min during oxide growth, hence they would be expected to suffer impact damage as well as having a thin sputtered In203 film coating the hemispherical oxide structures. This was cited as the reason for the poorer photoanodic response of the plasma grown films compared to those thermally grown. Based on this result it was estimated that geometry and improved solid-state properties were each responsible for =50% of the improvement of the rough thermally grown films over the flat reactively sputtered oxide films. In this note we provide direct evidence confirming that half of the improvement of the thermally grown films over the reactively sputtered films is due to improved solid-state properties.
doi:10.1149/1.2096460 fatcat:coxpf53gtnh5jlc2ktvhsmn2pq