Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 49: Metal Substrates: Structure, Epitaxy and Growth
O 49.3: Vortrag
Mittwoch, 18. März 2015, 11:00–11:15, MA 042
Intermixing of Pt and Cu atoms in PtCu/Ru(0001) surface alloys — •Luis Mancera1, Axel Groß1, Albert Engstfeld2, Andreas Bensch2, and R. Jürgen Behm2 — 1Institute of Theoretical Chemistry, Ulm University, D-89069 Ulm, Germany — 2Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany
In this contribution, we report on a joint theoretical and experimental study addressing model surface catalysts consisting of bimetallic PtCu surface alloys formed on a Ru(0001) substrate. The PtCu/Ru(0001) surface is obtained by deposition of Pt onto a previously prepared monolayer of Cu on Ru(0001) surface. In spite of the high stability of Ru(0001) that prevents exchange of Cu or Pt atoms with the substrate, Ru(0001) can still induce strain on the deposited Cu layer, due to the different lattice parameter, and thus modulate the formation of the PtCu alloy. Using STM imaging, it has been observed that the surface alloy is formed following a specific nucleation behavior that shows an atypical island density increase with growing Pt coverage. Here we apply periodic density functional theory (DFT) calculations to study various situations for atom diffusion on different surface alloy configurations in order to elucidate the origin of those nucleation patterns. We determine the stability of PtCu surface alloys and address the diffusion of Pt and Cu atoms on PtCu/Ru(0001) as well as Pt-Cu atom-exchange processes that lead to the formation of these alloys. Based on these findings, the effect of Pt substitutional atoms in the nucleation is discussed.