Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 82: Nanostructure at Surfaces: Dots and Clusters

O 82.2: Vortrag

Donnerstag, 19. März 2015, 10:45–11:00, MA 043

Ripening mechanisms of supported size-selected clusters — •Fabian Knoller, Michael König, Yves Fukamori, Friedrich Esch, and Ueli Heiz — Technische Universität München, Chair of Physical Chemistry, Lichtenbergstr. 4, 85748 Garching, Germany

Truly monodisperse clusters give an unprecedented access to the investigation of ripening in the non-scalable size regime. Here, the ripening dynamics of individual Pd19 clusters have been studied on a strongly interacting Rh(111) surface and on a weakly interacting supported, periodically wettable Moiré-graphene film [1]. Whereas on the former substrate Ostwald ripening is observed in series of STM images at room temperature, the latter shows Smoluchowski ripening at slightly elevated temperatures of about 323 K. In both cases, the lateral resolution is sufficient to detect isomerization processes that influence the ripening kinetics: shape-dependent atom detachment linked to atom diffusion, respectively height fluctuations linked to cluster diffusion. These movements act intermittently, on much faster time scales than the mean ripening process. We try to tackle this experimental problem by two additional STM measurement techniques, implemented by one electronic device: With FastSTM, time series with a temporal resolution of up to now 10 frames/s have been gained, while Atom Tracking allows for lateral and vertical determination of the cluster maxima with a time resolution down to 5 ms and a lateral resolution below atomic dimensions.

[1] Y. Fukamori, M. König, B. Yoon, B. Wang, F. Esch, U. Heiz and U. Landman, ChemCatChem 5 (2013) 3330-3341