Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 36: Postersitzung (Elektronische Struktur, Grenzfl
äche fest-flüssig, Halbleiteroberfl
ächen und -grenzfl
ächen, Nanostrukturen, Oberfl
ächenreaktionen, Teilchen und Cluster, Struktur und Dynamik reiner Oberfl
ächen)

O 36.7: Poster

Montag, 7. März 2005, 15:00–18:00, Poster TU F

Surface reconstruction effects on the surface state on noble metals — •Azzedine Bendounan, Frank Foster, Johannes Ziroff, Felix Schmitt, and Friedrich Reinert — Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

Noble metal surfaces (Cu, Ag and Au) in (111)-orientation are characterized by the existence of Shockley states which appear in the projected band L gap and form a quasi bi-dimensional system. Our photoemission experiments at low temperature (20 K) with very high energy and angle resolution give precise parameters characterizing the band dispersion of these states (energy of bottom of the surface band, effective mass and hole lifetime) which can be compared to the theory. Here, we present e.g. a study on the photoemission line-shapes of ultra-thin Ag films on Cu(111). Depending on the deposition temperature, the first Ag monolayer surface displays two typical 9×9 reconstructions resulting of the large lattice mismatch between Cu and Ag. At low temperature, the Ag monolayer forms an unstrained hexagonal moiré structure defined as a modulation resulting from the superposition of the two commensurate Ag and Cu lattices. Several Ag atoms are in energetically unfavorable on-top positions leading to strongly stressed Cu regions in the substrate. At room temperature, the surface presents a triangular corrugation interpreted as the introduction of a few Cu vacancies. It was shown that the bottom band energy of surface state depends on the type of superstructure present at the surface. In addition, we investigate the lifetime evolution in these highly-ordered reconstructions.