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          Institute: Fritz-Haber-Institut     Collection: Molecular Physics     Display Documents

ID: 234765.0, Fritz-Haber-Institut / Molecular Physics
Identification of Subsurface Oxygen Species Created during Oxidation of Ru(0001)
Authors:Blume, Raoul; Niehus, Horst; Conrad, Horst; Böttcher, Artur; Aballe, Lucia; Gregoratti, Luca; Barinow, Alexei; Kiskinova, Maya
Date of Publication (YYYY-MM-DD):2005-07-06
Title of Journal:Journal of Physical Chemistry B
Journal Abbrev.:J. Phys. Chem. B
Issue / Number:29
Start Page:14052
End Page:14058
Copyright:2005 American Chemical Society
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The oxidation states formed during low-temperature oxidation (T < 500 K) of a Ru(0001) surface are identified with photoelectron spectromicroscopy and thermal desorption (TD) spectroscopy. Adsorption and consecutive incorporation of oxygen are studied following the distinct chemical shifts of the Ru 3d5/2 core levels of the two topmost Ru layers. The evolution of the Ru 3d5/2 spectra with oxygen exposure at 475 K and the corresponding O₂ desorption spectra reveal that about 2 ML of oxygen incorporate into the subsurface region, residing between the first and second Ru layer. Our results suggest that the subsurface oxygen binds to the first and second layer Ru atoms, yielding a metastable surface "oxide", which represents the oxidation state of an atomically well ordered Ru(0001) surface under low-temperature oxidation conditions. Accumulation of more than 3 ML of oxygen is possible via defect-promoted penetration below the second layer when the initial Ru(0001) surface is disordered. Despite its higher capacity for oxygen accumulation, also the disordered Ru surface does not show features characteristic for the crystalline RuO₂ islands. Development of lateral heterogeneity in the oxygen concentration is evidenced by the Ru 3d5/2 images and microspot spectra after the onset of oxygen incorporation, which becomes very pronounced when the oxidation is carried out at T > 550 K. This is attributed to facilitated O incorporation and oxide nucleation in microregions with a high density of defects.
External Publication Status:published
Document Type:Article
Communicated by:Gerard Meijer
Affiliations:Fritz-Haber-Institut/Molecular Physics
External Affiliations:Institut für Physik der Humboldt-Universität, Newtonstrasse 15, 12489 Berlin, Germany;
Institut für Physikalische Chemie, Universität Karlsruhe, Kaiserstrasse 12, 76131 Karlsruhe, Germany;
Sincrotrone Trieste, AREA Science Park-Basovizza, Trieste-34012, Italy
DOI:10.1021/jp044175x S1089-5647(04)04175-6
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