par McEwen, Jean-Sabin ;Gaspard, Pierre ;Denecke, Reinhard;Streber, Regine;Traenkenschuh, Barbara;Schoeck, Johannes;Papp, Christian;Steinrueck, Hans-Peter
Référence ecoss26(August 30 2009 - September 4 2009), The 26th European Conference on Surface Science, page (207)
Publication Publié, 2009-08-30
Abstract de conférence
Résumé : Ultrathin, monatomic metal layers on metallic substrates represent two-dimensional system with novel electronic and chemical properties that are not present on neither of the parent metal surfaces [1]. Here we report a combined theoretical and experimental study concerning the properties of Ag on regularly stepped Pt(355) and Pt(322) surfaces in the presence of CO. Experiments were performed using high-resolution X-ray photoelectron spectroscopy. A detailed understanding of these experimental results is then provided by ab intio density functional theory calculations. When 0.2 ML of Ag is initially deposited at 300 K on Pt(355), a Ag nanowire is formed at the lower Pt step edges. This apparent blocking of the step sites by Ag results in a change in the CO adsorption behavior. In particular, we demonstrate theoretically for low CO coverages that the resulting C 1s core level binding energy of CO at Pt step sites is equal to the one for CO at terrace on-top sites in the presence of Ag, in contrast to the Ag free case [3]. At higher CO coverages we show that the formation of embedded Ag clusters within the upper terrace is induced, thus freeing up part of the original Pt step sites and, thus, reverting the C 1s core level binding energy back to its original value [2]. We compare our results to the geometrically similar Pt(322) surface, which only differs from Pt(355) by (100) instead of (111) oriented steps. It shows significant differences with respect to its interaction with Ag and CO, as it was already found to be the case in the absence of Ag [3]. In particular, a deeper embedding of the Ag islands within the upper Pt terrace is found. [1] J. G. Chen et al., Surf. Sci. Rep. 63 (2008) 201. [2] R. Streber et al., submitted to J. Chem Phys. (2009). [3] B. Traenkenschuh et al., Surf. Sci. 610 (2007) 1108.