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O: Fachverband Oberflächenphysik

O 20: Nanostructures at Surfaces II

O 20.5: Vortrag

Montag, 31. März 2014, 17:00–17:15, WIL B321

Electron Quantization Effects in Pristine and Isophorone-Modified Gold Nano-Islands on MgO Thin Films — •Christian Stiehler, Wolf-Dieter Schneider, Niklas Nilius, and Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

Electron quantization is a fundamental phenomenon that accompanies the transition from bulk metals to nanoclusters. The associated opening of a gap at the Fermi level crucially affects various properties of the nanostructures, e.g. its electrical and optical behavior and its performance in catalytic reactions [1]. By using low-temperature STM and related spectroscopy, we have investigated the electronic structure of 2D Au islands on MgO/Ag(001) thin films, containing between 50-200 atoms [2]. The bare islands exhibit characteristic quantum well states (QWS), arising from the spatial confinement of the Au-6p-orbitals. To explore the impact of molecular adsorption on this quantized structure, we have attached small quantities of isophorone (C9H14O) onto the Au islands. For ultra-small aggregates, we find a formation of Au-isophorone hybrid structures with clear fingerprints for the formation of covalent bonds between the two species. For larger islands, preferential adsorption of the molecules along the cluster perimeter is observed as well as a rigid downshift of the Au QWS that can be understood in terms of electron donation to the isophorone.

[1] M. Valden, X. Lai, D. W. Goodman, Science 281, 1647 (1998)

[2] C. Stiehler, Y. Pan, W.-D. Schneider, P. Koskinen, H. Häkkinen, N. Nilius, H.-J. Freund, PRB 88, 115415