AVS 53rd International Symposium
    Surface Science Friday Sessions
       Session SS-FrM

Paper SS-FrM11
Atomic Structure of the MgO(111)-(@sr@3x@sr@3)R30° Phase by Direct-Method Analysis of Surface X-Ray Diffraction Data

Friday, November 17, 2006, 11:20 am, Room 2002

Session: Oxide Surfaces and Interfaces
Presenter: S.S. Parihar, University of Wisconsin-Milwaukee
Authors: S.S. Parihar, University of Wisconsin-Milwaukee
H.T. Johnson-Steigelman, University of Wisconsin-Milwaukee
P.F. Lyman, University of Wisconsin-Milwaukee
V.L. Shneerson, University of Wisconsin-Milwaukee
R. Fung, University of Wisconsin-Milwaukee
D.K. Saldin, University of Wisconsin-Milwaukee
F.U. Renner, ESRF, Grenoble, France
T.-L. Lee, ESRF, Grenoble, France
J. Zegenhagen, ESRF, Grenoble, France
Correspondent: Click to Email
Polar-terminated oxides, where the bulk stacking produces a net dipole moment perpendicular to the surface, exhibit a rich set of energy-lowering mechanisms at the vacuum interface. For example, the polar oxide surface MgO(111) is known to undergo several air-stable reconstructions, including p(2x2) and (@sr@3x@sr@3)R30° phases. The observed periodicity depends on O partial pressure and temperature. The (@sr@3x@sr@3)R30° phase has been the subject of several structural investigations,@footnote 1,2@ but agreement has not been reached on a unique structure. We report on a structural investigation of the MgO(111)-(@sr@3x@sr@3)R30° reconstruction by surface x-ray diffraction. Our direct-methods analysis@footnote 3@ reveals maxima in the surface electron density. The atomic model suggested by the analysis can then be refined using the conventional @chi@@super 2@ process. For the MgO(111)-(@sr@3x@sr@3)R30° phase, we observe 1/3 ML of adatoms, and 2/3 ML vacancies. Implications for structural models via conventional refinement will be discussed. @FootnoteText@ @footnote 1@ R. Plass et al., Phys. Rev. Lett. 81, 4891 (1998).@footnote 2@ A. Subramanian et al., Phys. Rev. Lett. 92, 026101 (2004).@footnote 3@ P. F. Lyman et al., Surf. Sci. 600, 424 (2006).