Regensburg 2004 – scientific programme
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O: Oberflächenphysik
O 18: Adsorption an Oberflächen I
O 18.6: Talk
Tuesday, March 9, 2004, 12:30–12:45, H38
Surface Strain versus Substrate Interaction in Heteroepitaxial Metal Layers: Pt on Ru(0001) — •Peter Jakob1,2, Andreas Schlapka2, Ulrich Käsberger2, Markus Lischka2, and Axel Groß2 — 1Fachbereich Physik, Philipps Universität Marburg, 35032 Marburg, Germany — 2Physik-Department, Technische Universität München, 85747 Garching, Germany
Using STM, FT-IRAS and TDS, the effect of strain at an epitaxially grown Pt/Ru(0001) overlayer on the adsorption of various adsorbates has been studied. These effects are of strong current interest since they might provide a means of manipulating adsorption properties quite significantly. For pseudomorphic bimetallic layers the residual influence of the substrate and of the lattice strain within the deposited film produce a combined effect on the adsorbed species and it is difficult to uniquely separate their consequences. By studying the adsorption of CO on increasingly thicker layers of Pt deposited on Ru(0001), the influence of surface strain on the adsorption energy has now been disentangled from the residual chemical interaction with the substrate: whereas the electronic influence of the substrate dominates for thin films (1-2 layers) and vanishes for >3 Pt layers, strain related effects due to the 2.5% lattice mismatch of Pt and Ru remain active for thicker pseudomorphic overlayers and are only gradually released for n ≥ 5 Pt layers by means of formation of dislocation networks. Electronic structure calculations confirm the experimental observations, in particular, the dramatic decrease of the CO adsorption energy on a single Pt layer which is caused by the strong Pt-Ru interlayer coupling.