Epitaxial growth of ultrathin layered oxide films: MgO on NiO/Mo(100)

Abstract

Ultrathin epitaxial films of MgO(100) have been grown on NiO(100) films on a Mo(100) substrate. ISS results demonstrate that the NiO surface is almost completely masked for MgO coverages of 2 ML, and LEED studies confirm that the growth of MgO is epitaxial. The electronic structure probed by ELS demonstrates the development of MgO surface band structure through the sequential appearance of MgO transitions, but there are no transitions apparent which involve interface states. Increasing the thickness of the MgO overlayer on NiO induces an upward shift in the Ni(2p 3 2 ) XPS binding energy, with a shift of 1.0 eV for 7.5 ML of MgO, indicating that there is transfer of negative charge from the MgO to the NiO. Our findings for the growth of MgO on NiO demonstrate the feasibility of synthesis and study of ordered, layered, mixed oxide films only a few Å thick.