Strong Visible‐Light Absorption and Hot‐Carrier Injection in TiO₂/SrRuO₃ Heterostructures

Abstract Correlated electron oxides prove a diverse landscape of exotic materials' phenomena and properties. One example of such a correlated oxide material is strontium ruthenate (SrRuO₃) which is known to be a metallic itinerant ferromagnet and for its widespread utility as a conducting electrode in oxide heterostructures. We observe that the complex electronic structure of SrRuO₃ is also responsible for unexpected optical properties including high absorption across the visible spectrum (commensurate with a low band gap semiconductor) and remarkably low reflection compared to traditional metals. By coupling this material to a wide band gap semiconductor (TiO₂) we demonstrate dramatically enhanced visible light absorption and large photocatalytic activities. The devices function by photo‐excited hot‐carrier injection from the SrRuO₃ to the TiO₂ and the effect is enhanced in thin films due to electronic structure changes. This observation provides an exciting new approach to the challenge of designing visible‐light photosensitive materials.