Karsten Harbauer

α-Fe2O3 films for photoelectrochemical water oxidation – insights of key performance parameters

We report the deposition of ultra-thin α-Fe2O3 (hematite) films on fluorine-doped tin oxide (FTO) substrates using radio frequency (RF) sputtering, and the investigation of their photoelectrochemical (PEC) performance towards water oxidation. By varying the deposition pressure and time, the film microstructure and morphology could be optimized. The best hematite films having a thickness of about 50 nm exhibited a photocurrent density of 0.59 mA cm−2 at U = 1.23 V vs. RHE and 1.92 mA cm−2 at U = 1.85 V using a tungsten halogen lamp of 40 mW cm−2 light intensity in the wavelength range from 300 to 600 nm. These values are comparable or even higher than those ever measured hematite films (undoped and having no co-catalyst deposited on top of the electrode). Further measurements were explored to investigate the limiting factors in our films for possibly approaching their predicted PEC properties. A detailed analysis reveals that a slow water oxidation reaction and a trapping of charges on the surface, especially at the potential below 1.4 V, are obviously the reasons for the limited PEC performance.

Ion-energy distributions at a substrate in reactive magnetron sputtering discharges in Ar/H2S from copper, indium, and tungsten targets

Ion-energy distributions from copper, indium, and tungsten targets were measured during reactive sputtering in argon-hydrogen sulfide (H2S) mixtures, since reactive magnetron sputtering of sulfides from metallic targets is of increasing interest, especially for photovoltaic applications (buffer and absorber layers, i.e., CuInS2, In2S3, or WS2). The mass spectra of the ions show a wide range of molecules HxSn derived from H2S by plasma-assisted attachment both for positive (n≤9) and for negative (n≤6) ions. From the copper and the indium targets metallic ions (Cu+, In+) could be detected. While tungsten and indium sulfur compounds were found, copper does not form compounds with sulfur, caused by its lower chemical reactivity. Positive (Ar+, S+, W+, Cu+, In+, etc.) as well as negative ions (S−, InS−, WS3−) were measured for dc and rf (27 MHz) plasma excitations. The positive ions originate mainly from the plasma in front of the substrate and exhibit energies of about 12 eV for the dc and 18 eV for the rf di...

A multifunctional plasma and deposition sensor for the characterization of plasma sources for film deposition and etching

Our recently reported multifunctional plasma and deposition sensor [Welzel et al., Appl. Phys. Lett. 102, 211605 (2013)] was used for the characterization of two different plasma sources: a magnetron sputtering deposition source and an ion beam source. The multifunctional sensor, based on a conventional quartz crystal monitor (microbalance) for mass increase/decrease measurements, can measure quasi-simultaneously the deposition/etching flux, the energy flux, and the charged particle flux. By moving the sensor or the plasma source stepwise against each other, the lateral (radial) flux profiles of the different sources can be measured with a lateral resolution of about 8 mm, the diameter of aperture in front of the quartz crystal. It is demonstrated that this compact and simple multifunctional sensor is a versatile tool for the characterization of different kinds of plasma sources for deposition and etching purposes. By combining the different measured quantities, the ion-to-neutral ratio and the mean energ...

Author Correction: Highly (001)-textured p-type WSe 2 Thin Films as Efficient Large-Area Photocathodes for Solar Hydrogen Evolution

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.