Photoelectrochemical Properties of Sputtered and Plasma‐Oxidized Iron Oxide Films

Abstract

The results for iron oxide, thin film (∼500Å) electrodes, formed both by reactive sputtering from an iron target and by plasma oxidation of a sputter‐deposited iron film, are reported. The reactively sputtered electrodes were formed by deposition onto sputter‐deposited films of both iron and conducting indium tin oxide (ITO), while the plasma oxidized electrodes were formed with ITO only. The performance of the electrodes as photoanodes for evolution was found to be strongly dependent on a number of fabrication parameters, the best results being achieved for films formed on ITO and then vacuum annealed, both at 350°C. In this case, the performance matched or exceeded that reported in the literature for other methods of fabrication of polycrystalline iron oxide. Annealing these films in oxygen resulted in a decrease in photocurrent by a factor of three to four, as well as a 0.7 V suppression of the photocurrent onset potential. The effect was reversed on reannealing in vacuo. Postfabrication treatment of electrodes in various aqueous solutions was found to effect their performance significantly. More specifically, a substantial enhancement of the photocurrent in the onset region was achieved by treatment in a boiling KSCN solution. Mott‐Schottky plots and conductivity measurements are presented to illuminate these phenomena.