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).
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