Epitaxial Growth of BaSnO$_{3}$ using Hybrid Molecular Beam Epitaxy*

Using co-deposition of a chemical precursor for Sn, a solid source for Ba and an RF plasma source for oxygen, we have extended the hybrid MBE approach for the growth of stoichiometric BaSnO$_{3}$. First, we present a detailed growth study of SnO$_{2}$ on r-plane sapphire as a function of Sn flux, oxygen pressure and substrate temperature. High-resolution x-ray diffraction (HRXRD) and AFM showed single phase, epitaxial SnO$_{2}$ films and smooth surfaces, respectively. Three growth regimes were identified: reaction-, flux- and desorption-limited with increasing substrate temperature. Further study at constant substrate temperature revealed growth rate increases first and then becomes constant with increasing tin flux. We will then present a comprehensive study of the growth of phase-pure, smooth epitaxial BaSnO$_{3}$ films on SrTiO$_{3}$. HRXRD of 5nm BaSnO$_{3}$ on SrTiO$_{3}$ using synchrotron radiation suggest that films grow mostly coherent with out-of-plane lattice parameters of 4.20-4.25{\AA} for different cation flux ratios, remarkably similar to the calculated value of 4.26{\AA} using elastic tensors assuming BaSnO$_{3}$ grows coherent on SrTiO$_{3}$. Strain relaxation, stoichiometry control and their roles on the electronic transport will be discussed.