CO adsorption on epitaxially grown Pt layers on Ru(0 0 0 1) |
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Authors: | P Jakob A Schlapka |
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Institution: | a Fachbereich Physik und Wissenschaftliches Zentrum für Materialwissenschaften der Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany b Physik-Department E20, Technische Universität München, James-Franck-Str., D-85747 Garching, Germany |
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Abstract: | The adsorption of CO on epitaxially grown Pt films of variable thickness has been studied using infrared-absorption spectroscopy, scanning tunnelling microscopy and thermal desorption spectroscopy. Depending on the number of pseudomorphic Pt layers (NPt = 1-4) the internal and external CO stretching modes (νC-O and νPt-CO, respectively) display characteristic frequency shifts due to the vanishing influence of the underlying Ru(0 0 0 1) substrate and Pt/Ru interface. For thicker layers (NPt ? 5) when this influence has become negligible, the compressive stress within the Pt film is gradually relieved, leading to a dislocation network. The structural heterogeneity during the ongoing relaxation process of the Pt film is reflected in the νC-O line shape; no line broadening is observed for either pseudomorphic or very thick films (NPt ? 15). For NPt ? 3 the adsorption of CO on Pt/Ru(0 0 0 1) films closely resembles CO on Pt(1 1 1), with residual deviations in line position and desorption temperatures gradually converging to zero. |
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Keywords: | Vibrational spectroscopies Ruthenium Platinum Carbon monoxide Low index single crystal surfaces Epitaxy Surface stress |
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