Structure of the hydrogen-stabilized MgO(111)-(1x1) polar surface: Integrated experimental and theoretical studies
- Department of Physics and Laboratory for Surface Studies, University of Wisconsin Milwaukee, P. O. Box 413, Milwaukee, Wisconsin 53201 (United States)
- Fundamental Science Directorate, Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352 (United States)
The surface structure of MgO(111)-(1x1) 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 (1x1) polar surface periodicity is observed both after 800 deg. 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 1x1 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 0.98A. The in-plane O and Mg positions fit regular rocksalt sites, the distance between the topmost O and Mg plane is 1.04 A, contracted by {approx}14% with respect to bulk MgO distance of 1.21 A, 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.
- OSTI ID:
- 20666261
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 11 Vol. 71; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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