Precise composition control and cation nonstoichiometry in La-doped BaSnO3 thin films grown by MOCVD

ABSTRACT La:BaSnO3 has recently emerged as an outstanding perovskite oxide material due to its high electron mobility. To-date, lower electron mobility in thin films compared to the single-crystal are discussed in terms of the presence of dislocations, nearly neglecting the role of cation nonstoichiometry. However, by controlling Sn/Ba compositional ratio, we demonstrate the significance of stoichiometry and resulting point defects on microstructure, morphology, electrical properties, and Raman defect modes in epitaxial La:BaSnO3 films. A narrow compositional window is demonstrated to yield high mobility and smooth morphology in La:BaSnO3 thin films using the metalorganic chemical vapor deposition. The room temperature electron mobility of 121 cm2V-1s-1 and 85 cm2V-1s-1 was achieved on SrTiO3 and MgO substrates, respectively. Correlation between the lowering of the A1g soft mode near 140 cm−1 frequency and increase in the carrier mobility is demonstrated by Raman spectroscopy analysis. It was suggested that the position of this soft mode might be employed as a marker band for probing the electrical properties of La-doped BaSnO3 perovskites.