Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 75: Fundamentals of Catalysis I
O 75.4: Vortrag
Donnerstag, 4. April 2019, 11:30–11:45, H5
Observing diffusion and morphology changes of small metal clusters via scanning tunneling microscopy — •Barbara A J Lechner, Ke Zhang, Alexander Bourgund, Fabian Knoller, Ueli Heiz, and Friedrich Esch — Department of Chemistry & Catalysis Research Center, Technical University of Munich, Lichtenbergstr. 4, D-85748 Garching
Metal clusters are partway between molecular and bulk systems and thus exhibit special physical and chemical properties: Atoms can rearrange within a cluster to form different structural isomers, clusters of different size can exhibit a different diffusivity across the same support. Here, we show how scanning tunneling microscopy (STM) can be used to investigate such dynamical behavior of individual clusters. By operating our STM with a specially developed FastSTM add-on module, we followed steady state diffusion of Pdn (1≤ n ≤ 19) clusters and atoms inside the pore of a hexagonal boron nitride nanomesh on Rh(111). While atoms diffuse along the rim of a pore, a small cluster experiences a corrugation in the potential energy landscape and jumps between six sites around the center of the pore. Furthermore, we observed reversible cluster isomerization in situ. In another example, we observed an irreversible decrease in apparent height of Ptn clusters supported on an Fe3O4(001) single crystal surface with increasing temperature. Such a morphological change without concomitant changes in cluster coverage suggests that the cluster-support interface changes with temperature, possibly favoring flattened clusters over spherical ones.