Oxidation of Mg atomic monolayer onto silicon: A road toward MgOx/Mg2Si (11-1)/Si (100) heterostructure

Surface interfaces of thin magnesium oxide films elaborated onto Si(100)-(2 × 1) substrates were characterized using scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy, atomic force microscopy, and high-resolution transmission electron microscopy. We report that a flat and highly homogeneous magnesium oxide with well-defined interfaces could be grown at room temperature (RT) by repeating alternate adsorption of Mg atomic monolayer and O2 on Si(100). RT oxidation process of the first Mg monolayer plays a crucial role as driving force allowing a partial decomposition of amorphous ultra-thin Mg2Si at the Mg/Si interface to form more magnesium oxide in the surface. This process induces crystallization of the interfacial Mg2Si thin film and then gives arise to an unexpected MgOx/Mg2Si(11-1)/Si(100) heterostructure. MgOx monolayer displays a band gap of about 6 eV and exhibits a weak RMS roughness on large areas.