Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Metal subtrates: Adsorption of O and/or H
O 27.4: Vortrag
Dienstag, 23. März 2010, 11:15–11:30, H42
Surface stress driven population of an "unusual" adsorption site — •Zhen Tian1, Dirk Sander1, Holger Meyerheim1, Larissa Niebergall1, Nikolay Negulyaev2, Katayoon Mohseni1, Valeriy Stepanyuk1, and Jürgen Kirschner1 — 1Max-Planck-Institute of Microstructure Physics,Halle, Germany — 2Fachbereich Physik,Martin-Luther-Universität, Halle
Adsorption on (001) surfaces of fcc metals often leads to the population of the fourfold hollow site. This is not the case for small coverage of O on Ir(001), where adsorption on bridge sites is observed[1]. We perform combined surface X-ray diffraction (SXRD) [2], and adsorbate-induced surface stress measurement to elucidate the correlation between structure, stress and adsorption site. We find from SXRD that at 550 K up to a coverage of 0.5 O adsorbs in the unusual bridge site, whereas for θO > 0.5, the hollow sites are populated in addition. Our calculations offer an explanation for hollow site adsorption, as O-adsorption for θO > 0.5 in bridge sites would induce a prohibitively large lattice corrugation. Our stress measurements reveal a compressive surface stress change of −2.2 N/m for the population of both p(1×2) and hollow sites at a total coverage of 0.75. Our experimental results on the atomic structure and the O-induced surface stress change are supported by ab initio calculations. [1] K. Johnson, Q. Ge, S. Titmus, and D. A. King, J. Chem. Phys. 112 (2000) 10460. [2] We thank the staff at ID-03, E.S.R.F., Grenoble for expert support.