Heteroepitaxial Growth of MgO Films on NiO(100) Single Crystal Surfaces

Epitaxial MgO layers were grown on cleaved NiO(100) single crystal surfaces. The less than 1% lattice mismatch between MgO and NiO allows almost ideal epitaxy of MgO at 100°C. The epitaxial films were created by dosing Mg onto stoichiometric NiO(100) both in ultra-high vacuum (UHV) and in an O2 atmosphere (5×10−7 Torr). Chemical interactions at the resulting interfaces were studied using XPS. When Mg is dosed onto NiO(100) in UHV, MgO forms by interacting with oxygen anions in the NiO substrate thereby reducing the nickel cations. Metallic Mg layers begin to form upon subsequent dosing. When Mg is deposited in O2, epitaxial MgO(100) layers grow to a thickness of at least 50Å as confirmed by in situ RHEED and LEED observations. Negligible intermixing between the MgO and NiO is observed during growth at 100°C and on subsequent annealing in UHV up to 600°C.