Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Organic films and electronics, photoorganics; Nanostructures; Plasmonics and nanooptics, Surface chemical reactions and heterogeneous catalysis, Surface dynamics )

O 36.84: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B2

High-Frequency Vibrational Modes of Cold-Deposited Copper Adatoms on Low-Index Copper Surfaces — •Jan Pischel, Olaf Skibbe, and Annemarie Pucci — Kirchhoff-Institut für Physik, Im Neuenheimer Feld 227, D-69120 Heidelberg

Vicinal low-index metal surfaces are known to give rise to vibrational modes with frequencies well above the bulk phonon band [1,2]. Low-coordinated atoms at steps and kink sites which relax with respect to their bulk position, but also with respect to their regular surface position, have been identified as originators of these high-frequency modes [2]. If the surface, the steps and the kinks are thought of as "perturbations of increasing complexity on an otherwise periodic system" [2], the next step would consequently be to investigate the vibrational properties of single adatoms.

For that purpose, we prepared copper surfaces with a well-defined degree of roughness under UHV by cold-depositing small amounts of copper on sputter-annealed low-index surfaces. Our HREEL-spectra of the rough Cu(111) and Cu(110) surfaces show indeed excitations at frequencies even higher than those observed on the vicinal surfaces. Since vibrations are playing a crucial role in the mediation of surface reactions [3], the existence of high-frequency vibrational modes on rough metal surfaces is expected to be relevant for a better understanding of catalytic reactions.

[1] H. Ibach and D. Bruchmann, Phys. Rev. Lett. 41:958–960, 1978.

[2] A. Kara et al., Phys. Rev. B 61:5714–5718, 2000.

[3] D.N. Denzler et al., Phys. Rev. Lett. 91:226102, 2003.