Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 53: Nanostructures at surfaces: Dots, particles, clusters III

O 53.1: Vortrag

Donnerstag, 26. März 2009, 15:00–15:15, SCH A215

One-Dimensionally Ordered Metal Cluster Arrays on Carburized W(110) — •Magdalena Bachmann, Martin Gabl, Norbert Memmel, and Erminald Bertel — Institute of Physical Chemistry, University of Innsbruck, A-6020 Innsbruck, Austria

The growth of noble (Ag, Au) and transition metal (Co) nanodots on the carburized tungsten (15x12)C/W(110) surface is studied by scanning tunneling microscopy (STM). At elevated temperatures for all metals small clusters are observed which are arranged with the periodicity defined by the template structure (1.4 x 3.1 nm2). The same adsorption sites are occupied by transition and noble metal clusters. Apart from these similarities also marked differences exist, in particular at higher coverages, when more material is deposited than can be adsorbed on the favorable cluster adsorption sites in each unit cell. Close to room temperature excess cobalt atoms nucleate as "interstitial" Co clusters, whereas Ag forms double-layer islands overgrowing the nanodots. At elevated temperatures in case of Co monolayer-high islands are observed, filling the free space between the clusters, whereas in case of Ag a transport of excess Ag atoms to clean tungsten terraces takes place, resulting in regular cluster growth on carbon-covered patches. Obviously, for Co the difference in adsorption strength between the more and the less favourable sites within each unit cell is less pronounced. The present results for Au contradict to some extend a recent STM study by Varykhalov et al. [Phys. Rev. B 77, 035412 (2008)]. Reasons for these discrepancies will be discussed.