Stoichiometry control in molecular beam epitaxy of BaSnO3

Abstract

La-doped $\mathrm{BaSn}{\mathrm{O}}_{3}$ films were grown on $\mathrm{DySc}{\mathrm{O}}_{3}$ substrates by molecular beam epitaxy using La, Ba, and $\mathrm{Sn}{\mathrm{O}}_{2}$ sources with and without additional oxidant, respectively. Lattice parameter measurements as a function of growth conditions show a reduced lattice parameter that is likely due to substitution of $\mathrm{S}{\mathrm{n}}^{2+}$ on the Ba site. The propensity for the antisite defect is discussed as being due to the combination of oxygen-poor, Sn-rich conditions and the dual valence of Sn. Although electron mobilities are highest for films with reduced lattice parameters, antisite defects will pose an upper limit to thin film mobility. Less Sn-rich conditions lead to the formation of another defect that causes a lattice expansion. The combined effects of these defects on the lattice parameter can compensate each other and cause the appearance of a stoichiometric lattice parameter for nonstoichiometric films with poor electrical behavior.