Structure of the hydrogen-stabilized MgO(111)(1×1) polar surface: Integrated experimental and theoretical studies

V. K. Lazarov, R. Plass, H-C. Poon, D. K. Saldin, M. Weinert, S. A. Chambers, and M. Gajdardziska-Josifovska
Phys. Rev. B 71, 115434 – Published 31 March 2005

Abstract

The surface structure of MgO(111)(1×1) bulk and thinned single crystals have been investigated by transmission and reflection high-energy electron diffraction, low-energy electron diffraction (LEED), and x-ray photoelectron and Auger electron diffraction. The (1×1) polar surface periodicity is observed both after 800 °C annealing in air and also after oxygen plasma cleaning and annealing in ultrahigh vacuum. The x-ray photoelectron spectroscopy and diffraction results were analyzed by simulations based on path-reversed LEED theory and by first-principles calculations to help distinguish between different mechanisms for the stabilization of this extremely polar oxide surface: (1) stabilization by adsorption of a hydrogen monolayer; maintaining the insulating nature of the surface and (2) stabilization of the clean O or Mg terminated 1×1 surface by interlayer relaxations and two-dimensional surface metallization. The analysis favors stabilization by a single OH layer, where hydrogen sits on top of the O ions with O-H bond distance of 0.98Å. The in-plane O and Mg positions fit regular rocksalt sites, the distance between the topmost O and Mg plane is 1.04 Å, contracted by 14% with respect to bulk MgO distance of 1.21 Å, while the interlayer separation of the deeper layers is close to that of bulk, contracted by less than 1%. The presence of a monolayer of H associated with the terminal layer of oxygen reduces significantly the surface dipole and stabilizes the surface.

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  • Received 20 July 2004

DOI:https://doi.org/10.1103/PhysRevB.71.115434

©2005 American Physical Society

Authors & Affiliations

V. K. Lazarov1, R. Plass1,*, H-C. Poon1, D. K. Saldin1, M. Weinert1, S. A. Chambers2, and M. Gajdardziska-Josifovska1,†

  • 1Department of Physics and Laboratory for Surface Studies, University of Wisconsin Milwaukee, P. O. Box 413, Milwaukee, Wisconsin 53201, USA
  • 2Fundamental Science Directorate, Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352, USA

  • *Current address: Sandia National Labs, M.S. 1310, P.O. Box 5800, Albuquerque, NM 87185, USA.
  • Electronic address mgj@uwm.edu

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Vol. 71, Iss. 11 — 15 March 2005

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