Berlin 2015 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 24: Metal substrates: Structure, epitaxy and growth (joint session with O)

DS 24.4: Vortrag

Mittwoch, 18. März 2015, 11:15–11:30, MA 042

Alloying and dealloying of Mg on the Ag(100) surface — •Marina Schuler, Pascal Ferstl, Lutz Hammer, and M.Alexander Schneider — Lst. für Festkörperphysik, FAU Erlangen-Nürnberg

Ultrathin oxide films on metal substrates play an important role in basic surface research and technological applications. Since these oxide films are often prepared via postoxidation of pre-deposited metal films, their structural properties may strongly influence the quality of the growing oxide. In this study we investigate the structures developing during Mg deposition on Ag(100) prior to oxidation to MgO by means of quantitative LEED and STM.

Submonolayers of Magnesium adsorbed at 90 K on top of the plain Ag(100) surface form an ordered (√5×√5)R arctan0.5 phase. Annealing to 150 K leads to an atomic reorganisation at the surface and a c(2×2) phase appears, which has been reported already [1]. The crystallographic structure of this c(2×2) phase is shown to be a bimetallic surface alloy by means of a quantitative LEED analysis: every second Ag atom of the toplayer is substituted by Mg, which relaxes outward by 0.13 Å. The Mg/Ag-c(2×2) structure persists further Mg deposition at elevated temperatures dissolving surplus Mg atoms into the underlying substrate layers. By offering 1·10^-7 mbar oxygen at 400 K the dissolved Mg is driven at the surface of the crystal again, forming MgO films of the corresponding thickness.
[1] C. Tegenkamp Appl. Surf. Sci. 151 40 (1999)