Harnessing Selective Exsolution of Sn Metal to Enhance Electrical Conductivity in Oxygen‐Deficient Perovskite Stannates
Daseob Yoon, Yujeong Lee, Gi‐Yeop Kim, Youngho Kang, Si‐Young Choi, Junwoo Son
Abstract
Abstract The 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 BaSnO 3−δ films after the reduction process so far. Here, a new strategy to enhance the electrical conductivity of BaSnO 3−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 BaSnO 3−δ films, interestingly, only Sn‐excess BaSnO 3−δ films show a dramatic increase of carrier concentration ( ∆ n 3D = 5–7 × 10 19 cm −3 ) after high‐temperature reduction; exceptionally high electrical conductivity (σ ≈ 6000 S cm −1 ) is achieved in reduced Sn‐excess (La, Ba)SnO 3−δ films, which exceed full activation of La dopants in untreated (La, Ba)SnO 3 . 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 n 3D in the BaSnO 3−δ matrix as a result of spontaneous charge transfer from the segregated β‐Sn metallic phase to BaSnO 3−δ . These original results propose a simple strategy to further increase electrical conductivity in perovskite oxide semiconductors by non‐stoichiometry‐driven metal exsolution.