Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 42: Poster Session II (Nanostructures at surfaces: arrays; Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: Other; Nanostructures at surfaces: Wires, tubes; Metal substrates: Adsorption of O and/or H; Metal substrates: Clean surfaces; Metal substrates: Adsorption of organic/bio moledules; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsorption of inorganic molecules; Metal substrates: Epitaxy and growth; Heterogeneous catalysis; Surface chemical reactions; Ab-initio approaches to excitations in condensed matter; Organic, polymeric, biomolecular films– also with adsorbates; Particles and clusters)

O 42.83: Poster

Wednesday, March 25, 2009, 17:45–20:30, P2

Structure and energetics of bimetallic surface confined alloys — •Andreas Bergbreiter¹, Ralf T. Rötter¹, Albert K. Engstfeld¹, Harry E. Hoster¹, Axel Groß², and R. Jürgen Behm¹ — ¹Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm — ²Institute for Theoretical Chemistry, Ulm University, D-89069 Ulm

The atomic distribution in a number of A_xB_1−x/B type surface alloys was determined by STM imaging with chemical contrast and statistically evaluated. Whereas in the systems Au_xPt_1−x/Pt(111), Ag_xPt_1−x/Pt(111), and Pd_xRu_1−x/Ru(0001) we find preferences for larger homoatomic aggregates, the atom distribution in Pt_xRu_1−x/Ru(0001) and Ag_xPd_1−x/Pd(111) is very close to a random one [1]. In Ag_xPd_1−x/Pd(111), our data show a small tendency towards clustering for x_Ag<0.5, whereas at x_Ag>0.5 this is reversed to a slight preference for heteroatomic neighborhoods. Based on these experimental results, we have derived effective cluster interaction energies for all surface alloys [2]. These allow us to calculate phase diagrams for the surface alloys that we compare to predictions from theoretical work and to the behaviour of the corresponding bulk systems. We also discuss in how far the different atom distributions affect chemical and catalytic properties of the surface alloys.
[1] H.E. Hoster et al., Phys.Chem.Chem.Phys 10 (2008) 3812.
A. Bergbreiter et al., Phys.Chem.Chem.Phys 9 (2007) 5127.