A Combinatorial Study of Photoelectrochemical Properties of Fe‐W‐O Thin Films

A continuous mixed Fe-W-O thin-films materials library was fabricated by means of reactive co-sputtering from elemental iron and tungsten targets in argon/oxygen. The materials library was screened for its local photoelectrochemical properties by using an automated optical scanning droplet cell. Local scanning electron microscopy (SEM) and electron-dispersive Xray spectroscopy (EDX) measurements of the materials library were performed to correlate the composition, morphology, and photocurrents. The iron content was varied in the range from Fe32W68Ox to Fe81W19Ox. A strong dependence of the film morphology and the measured photocurrents on the composition was observed with a maximal photocurrent from a measurement area containing 55 at% iron. The most photoactive area showed a porous structure with a high surface area. The bandgap values of these materials were assessed by photocurrent spectroscopy and showed a systematic variation of the bandgap values with the composition.