Harnessing Selective Exsolution of Sn Metal to Enhance Electrical Conductivity in Oxygen‐Deficient Perovskite Stannates

Abstract

AbstractThe versatile application of newly discovered oxide semiconductors calls for developing a simple process to generate conducting carriers. High‐temperature reduction treatment leads to electrical conduction in perovskite stannate semiconductors, but carrier concentration is poorly controlled and inconsistently reported in BaSnO3−δ films after the reduction process so far. Here, a new strategy to enhance the electrical conductivity of BaSnO3−δ films is demonstrated by exploiting selective exsolution of Sn metals in the perovskite framework. Due to strong dependence of conductivity on initial Sn/Ba cation ratio in the reduced BaSnO3−δ films, interestingly, only Sn‐excess BaSnO3−δ films show a dramatic increase of carrier concentration (∆n3D = 5–7 × 1019 cm−3) after high‐temperature reduction; exceptionally high electrical conductivity (σ ≈ 6000 S cm−1) is achieved in reduced Sn‐excess (La, Ba)SnO3−δ films, which exceed full activation of La dopants in untreated (La, Ba)SnO3. By multiple characterizations combined with theoretical calculation, it is disclosed that a small fraction of segregated β‐Sn nanoparticles is likely to contribute the additional source of n3D in the BaSnO3−δ matrix as a result of spontaneous charge transfer from the segregated β‐Sn metallic phase to BaSnO3−δ. These original results propose a simple strategy to further increase electrical conductivity in perovskite oxide semiconductors by non‐stoichiometry‐driven metal exsolution.