Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 74: Metal Substrates: Adsorption of O and/or H
O 74.1: Talk
Thursday, February 28, 2008, 15:00–15:15, MA 141
Structure determination for the W(100)-(2×2)-O surface phase — •Wolfgang Meyer, Kerstin Biedermann, Lutz Hammer, and Klaus Heinz — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen
For oxygen adsorbed on the W(100) surface and annealed at a temperature of 1000∘C a (2×2) reconstruction is observed for which an O coverage larger than 1.0 ML has been reported [1]. Although the existence of this surface phase has been known for long, its structure is still unknown. We investigated this W(100)-(2×2)-O phase by means of quantitative LEED. The analysis reveals that the surface comprises two coexisting domains with p(2×2) and p(2×1) order, respectively. The p(2×1) structure is the already known missing row reconstruction with 1 ML oxygen atoms residing in the three-fold sites along the tungsten chains [2]. The p(2×2) domain consists of a single W atom per (2×2) unit cell decorated by four O atoms. Another oxygen atom is located on top of the 3rd layer tungsten atoms, resulting in a total oxygen coverage of 1.25 ML for this domain. The surface is covered with the two domains at a fraction of 60 % for the (2×2) order and 40 % for the (2×1) order. The W(100)-(2×2)-O surface phase can be considered as a precursor for the (2×1) missing row structure which is fully developed for higher annealing temperatures.
[1] E. Bauer et al., Surf. Sci. 58 (1976) 517
[2] H. Yamazaki et al., Surf. Sci. 477 (2001) 174