Stressing Pd atoms: Initial oxidation of the Pd(110) surface

R. Westerström1, C. J. Weststrate1, A. Resta1, A. Mikkelsen1, J. Schnadt1, J. N. Andersen1, E. Lundgren1, M. Schmid2, N. Seriani3, J. Harl3, F. Mittendorfer3, G. Kresse3

1 Dept. of Synchrotron Radiation Research, Lund University, 22100 Lund, Sweden
2 Institut für Allgemeine Physik, Technische Universität Wien, 1040 Wien, Austria
3 Fakultät für Physik, Universität Wien, A-1090 Wien, Austria

Surf. Sci. 602 (2008) 2440-2447

We have investigated the oxygen induced structures of the Pd(110) surface in the pressure range of 10-5 - 10-3 mbar of oxygen, at a sample temperature of around 300 °C. These structures, denoted as "(7 × √3)" and "(9 × √3)", are studied in detail by the use of a combination of low-energy electron diffraction, scanning tunneling microscopy, high-resolution core level spectroscopy, and ab-initio simulations. Based on our data a model is proposed for these structures, containing segments of Pd atoms in the [1-10] direction, in which the Pd rows are decorated by O atoms in a zig-zag pattern. The segments are periodically separated by displaced Pd atoms. Density functional theory calculations show that the displacements reduce the oxygen-induced stress significantly, as compared to a structure with no displacements. The calculations also suggest that the new structures are stabilized by domain formation.

Corresponding author: R. Westerström. Reprints also available from M. Schmid (schmid< encoded email address >).

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