Simultaneous reduction of multi-dimensional defects in Sn-excess BaSnO3 epitaxial films induced by surface chemical reconstruction

Abstract

Multi-dimensional defects created by thermodynamic and mechanical condition strongly limit electron mobility by the scattering of charged carriers in semiconducting BaSnO3 (BSO) epitaxial films. Here, we demonstrate that the density of both extended and point defects in heteroepitaxial BSO films can be decreased simultaneously by exploiting surface phase instability and a subsequent redistribution of cations at thermal treatment under different oxygen chemical potentials. By delicately controlling both cation ratio and ambient oxygen partial pressure p(O-2), distinct surface topography and cation redistribution (i.e., BaO segregation or SnO evaporation) were observed along with effective healing of extended defects. Simultaneous control of extended and point defects in La-doped BaSnO3 (LBSO) films during treatment under reducing atmosphere decreased their scattering of charged carriers and yielded an increase in room-temperature electron mobility mu(e) by similar to 104% (55-112 cm(2) V-1 s(-1)) in initially Sn-excess LBSO films as a result of a complex interplay with the removal of Sn-related species at the surface. Our finding suggests a versatile strategy to further enhance electron transport of perovskite-type stannate films by exploiting chemical heterogeneity on the surface interfacing with the p(O-2)-controlled ambient.