Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 32: Metal Substrates I
O 32.8: Vortrag
Dienstag, 12. März 2013, 12:15–12:30, H42
Joint DFT and STM/LEED investigation of oxygen adsorption on Ir(100)-1x1 — •Anja Michl1,2, Pascal Ferstl3, Tobias Schmitt3, Lutz Hammer3, M. Alexander Schneider3, and Stefan Müller2 — 1Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany — 2Institute of Advanced Ceramics, Hamburg University of Technology, Hamburg, Germany — 3LS f. Festkörperphysik, Universität Erlangen-Nürnberg, Germany
We explore the structure and stability of oxygen overlayers on Ir(100)-1x1 by combining first-principles calculations using density functional theory (DFT) with LEED and STM. The energetics of various ordered superstructures with different adsorption sites and coverages θ are used to construct a surface phase stability diagram. Apart from the well-known (2×1)-br superstructure and a (hypothetical)(1×1)-br phase, we identify two more ground states, which are also characterized by oxygen atoms exclusively occupying bridge positions: a (3×1)-br structure at θ=0.33 ML and a (4×1)-3br with 3 O-atoms per unit cell at θ=0.75 ML. Both new phases are verified by experiment, whereby the (3×1)-br structure could be prepared as single phase all over the surface, while the (4×1)-3br was found only as small patches of locally higher coverage within the (2×1)-br phase. Moreover, periodically arranged 1D domain walls with locally reduced oxygen coverage are observed with STM. We compare different models for the atomic structure of the domain walls based on a shifted row reconstruction mechanism of the underlying iridium substrate.