Realization of an atomically flat BaSnO3(001) substrate with SnO2 termination

Abstract

Atomically flat terraces terminated by mostly single layer SnO2 are realized on the surface of a BaSnO3(001) substrate with a lateral dimension of about 3 × 3 mm2 by deionized water leaching and thermal annealing. Surface topography studies reveal that by controlling the annealing time and temperature, the topmost surface evolves from having chemically mixed termination to atomically flat terraces with a step height of one unit cell. The step bunching and kinked steps also depend sensitively on the out-of-plane and in-plane miscut angles. X-ray photoemission spectroscopy near the Ba3d5/2 and Sn3d5/2 states with variation in the electron emission angle confirmed that the topmost atomic layer of the BaSnO3−δ(001) surface mostly consisted of SnO2 rather than BaO. The present findings will facilitate the preparation of atomically flat BaSnO3(001) substrates, which will be useful in the studies of exploring possible two-dimensional electron gases at the interface between BaSnO3(001) and other oxides.