SrTiO₃ thin film photoanodes fabricated by combinatorial chemical beam vapour deposition: intricate connection between elemental composition and thin films' properties

In this research, we highlight an innovative combinatorial approach to explore the correlation between the elemental composition of SrTiO3 thin films and their photoelectrochemical characteristics for water splitting. Employing the Chemical Beam Vapor Deposition technique, we successfully synthesized SrxTiyOz thin films with varying Sr/Ti compositions, ranging from highly strontium cation deficient (Sr/Ti = 0.3) to rich (Sr/Ti = 2) films, in a single deposition process. A detailed examination of the near-stoichiometric range identified a narrow window wherein the crystalline perovskite structure was maintained. This enabled us to pinpoint the optimal strontium to titanium ratio composition between St/Ti = 0.8 and Sr/Ti = 1.2, resulting in the most efficient photoelectrode. The performance of these photoelectrodes was correlated with the physico-chemical properties of the SrxTiyOz films, as investigated through techniques such as X-ray diffraction, ultraviolet-visible absorption spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy.