Low-temperature growth of MgO by molecular-beam epitaxy

We have explored the epitaxial growth of MgO single crystals using separate ${\mathrm{O}}_2$ and Mg beams and also e-beam-evaporated MgO. The latter method is preferred as the incorporation efficiency of ${\mathrm{O}}_2$ turns out to be ∼${10}^{\mathrm{-}3}$ even at 200 °C in the former method. Excellent MgO grows by e-beam evaporation at temperatures down to 140 K (${\mathit{T}}_{\mathit{m}}$/20), in agreement with expectations of Yang and Flynn. Good surface quality is achieved in heteroepitaxy, even for the first few monolayers.