Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 82: Metal Substrates II
O 82.7: Vortrag
Donnerstag, 3. April 2014, 17:30–17:45, WIL A317
Local Adsorption Sites of Oxygen and Hydrogen on the Ir(100) surface — •Pascal Ferstl1, Lutz Hammer1, M. Alexander Schneider1, Florian Mittendorfer2, Md. Alif Arman3, Edvin Lundgren3, and Jan Knudsen3 — 1Lst f. Festkörperphysik, FAU Erlangen-Nürnberg, Germany — 2Inst. f. Angewandte Physik & CMS, TU Wien, Austria — 3Synchrotron Radiation Research, Lund, Sweden
The adsorption behavior of oxygen and hydrogen on transition metal surfaces is of fundamental importance for heterogeneous catalysis. In this high-resolution X-ray photoelectron spectroscopy study we investigated their adsorption on the Ir(100) surface in the whole accessible coverage range Θ=0−1.0. The investigation is complemented by LEED, STM and TDS measurements, as well as by DFT calculations, allowing the clear identification of different components in the XP-spectra of the various phases.
A detailed investigation of the Ir 4f7/2 line reveals that on the unreconstructed Ir(100)-1×1 surface both adsorbates are found to occupy exclusively bridge sites of the substrate. For the maximum coverage Θ=1.0 – in case of oxygen this can only be achieved by offering atomic species – every Ir surface atom is connected to two adsorbate atoms while for Θ=0.5 every two substrate atoms have to share one adsorbate. This leads to clear shifts in the Ir 4f7/2 core level energies. Series of spectra taken for various coverages achieved via successive thermal desorption can be explained by a superposition of spectra of these limiting structures and that for the finally reached clean, reconstructed 5×1 phase discarding any further local binding configuration.