Effect of Sr interlayer on the epitaxy and band alignment of MgO-buffered Si(100)

Magnesium oxide (MgO)-buffered silicon is an effective pseudo-substrate that enables the epitaxial integration of functional oxides on silicon. Its high thermal stability also serves as a good diffusion barrier that prevents silicon migration to the oxide layer and provides both electrical and optical isolation. We report on the process of forming epitaxial MgO thin films on Si(100) by molecular beam epitaxy using a Sr submonolayer to limit bulk Si oxidation even in the presence of oxygen. The films are characterized using x-ray diffraction, x-ray reflectivity, x-ray photoelectron spectroscopy, reflection-high-energy electron diffraction, scanning transmission electron microscopy, and electron energy loss spectroscopy. The in-plane epitaxial relationship is MgO 〈100〉||Si 〈100〉 with a 4:3 coincident site arrangement between the MgO and Si conventional unit cells. The effect of the Sr submonolayer on the band alignment between MgO and Si is also measured and theoretically modeled using first principles calculations.