Impedance Measurements and Photoeffects on Ni Electrodes

Depending on the electrode potential an n-type or a p-type semiconducting oxide can be present at a Ni electrode surface giving rise, respectively, to anodic or cathodic potocurrents under illumination. Impedance measurements show that a solid-state diffusion process, presumably of protons through the oxide film, dominates the impedance behavior for the charged electrode; for the discharged electrode, the impedance behavior is dominated by the space charge inside the p-type oxide. A flatband potential and donor density estimate could be made for the p-type semiconducting oxide.