Lateral Rutile/Anatase Biphase TiO ₂ Superlattice: Its Step‐Assisted Controllable Growth and Interfacial Structure

Abstract Rutile/Anatase (R/A) biphase TiO ₂ has superior photocatalytic performance than its single‐phase counterpart due to the effect of interface band alignment. However, two crucial issues remain unresolved: First, the controllable growth of epitaxial R/A TiO ₂ with unburied interfaces is extremely challenging. Second, the direction of electron flow is full of controversy since the atomic and electronic structures of the R/A interface have not been experimentally obtained. Here a controllable growth of lateral R/A biphase TiO ₂ superlattice on stepped LaAlO ₃ substrates is demonstrated. The R‐TiO ₂ nucleates at the steps of substrate while the A‐TiO ₂ grows on the terraces. It is revealed that the R/A interface has a built‐in electric field and a reduced band gap. Photogenerated electrons flow toward A‐TiO ₂ due to its higher electron affinity. The lateral R/A biphase TiO ₂ superlattice exhibits outstanding water‐splitting performance and may find applications in other fields. The strategy of step‐assisted growth of lateral biphase superlattice should be applicable for other compounds with polymorphs.