No abstract

The electrochemical and photoelectrochemical properties of sputtered films of TiO2∼1000Å thick, have been investigated using a variety of electrometric techniques, for films sputtered on cooled substrates in both pure oxygen and oxygen/argon mixtures. Good photoresponse was achieved only for films sputtered in pure oxygen and then only after a cathodic electrochemical treatment that results in a 10‐fold increase in photocurrent, but no change in the potential for photocurrent onset. Evidence exists for three modes of electrochemical incorporation of hydrogen in the films: (i) irreversible filling with hydrogen which becomes bound to the lattice and is probably responsible for the 10‐fold increase in photocurrent through trap‐filling mechanism; (ii) filling to the extent of one per 3.7Ti with hydrogen that can be removed at anodic potentials only when the film is under illumination. This hydrogen does not act as electron donor in the dark, but leads to a large increase in the dielectric constant of the film; and (iii) reversible filling with hydrogen under potential control. Interpretation of Mott‐Schottky plots is complicated by one or more of hydrogen incorporation, hydrogen adsorption, and dielectric saturation processes. However, the doping density is determined to be ≤1017 cm−3.

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 O2 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.

The photoelectrochemical properties of films of indium oxide formed in essentially three different ways are reported. These are (i) reactive sputtering of the oxide from an indium metal target, (it) thermal oxidation of thin indium metal films, also sputter deposited, and (iii) plasma oxidation of the same thickness of indium metal. While reactively sputtered films exhibit a maximum quantum efficiency -20% at 290 nm, similar to that achieved with single crystal In~O:~, the thermally oxidized films give -90% quantum efficiency at 310 nm. The bandgap energies as determined from photoelectrochemical studies were 2.8 eV (indirect) and 3.6 eV (direct) for all three types of films. The solid-state, optical, morphological, and photoelectrochemical properties of the three types of films are reported and compared. A major portion of the improvement of the thermally oxidized films over those reactively sputtered is morphological in nature, which suggests the possibility for substantial improvement of other photoelectrode materials utilizing the same effect.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-26 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-26 to IP

Durch Oxidation (O2, 30 min, 350°C) dünner In‐Metallfilme werden In2O3‐Filme von ca. 1000Å Dicke hergestellt und auf ihre photoelektrochemischen Eigenschaften untersucht.