Molecular Beam Epitaxy of MgO on Perovskite Substrates

Rock salt oxides are promising interface layer materials for the integration of multifunctional oxides with semiconductors (Si, SiC, and GaN). Although rock salt oxides were previously grown on a wide range of semiconductor (Si and GaAs) and oxide (LaAlO$_{3}$ and SrTiO$_{3})$ substrates, the influence of lattice mismatch on the crystalline quality of the films was not studied. MgO thin films were grown by molecular beam epitaxy on LSAT, LaAlO$_{3}$ and SrTiO$_{3}$ perovskite substrates to investigate the effects of lattice mismatch on the film crystal quality. Despite a lattice mismatch of $\sim $7.9{\%} and $\sim $9{\%}, respectively, epitaxial growth of MgO was achieved on SrTiO$_{3}$ and LSAT substrates. Films grown on LaAlO$_{3}$ substrates exhibiting a lattice mismatch of $\sim $10.5{\%} were polycrystalline, yet epitaxial MgO on LaAlO$_{3}$ was deposited after the introduction of a SrTiO$_{3}$ buffer layer. The effects of deposition rate, substrate temperature, ozone flux, SrTiO$_{3 }$buffer layer thickness and stoichiometry were also investigated. This work was supported by the Office of Naval Research under grants N00014-05-1-0238 and N00014-06-1-1018.