Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.70: Poster

Friday, March 4, 2005, 17:00–20:00, Poster TU D

Optical properties of silver cluster ensembles — •Hadj Mohamed Benia, Niklas Nilius, and Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin

By means of photon emission spectroscopy with an STM, we have studied the electromagnetic coupling in silver cluster ensembles. The ensembles were prepared by two techniques: (i) atom deposition on a thin alumina film in UHV and (ii) deposition of size-selected silver colloids, prepared by a reverse micelle technique, on gold and HOPG substrates. Silver on alumina grows with a very low cluster density. The corresponding cluster ensemble shows one plasmon resonance, indicative for weak cluster-cluster coupling. In contrast, measurements on dense colloidal cluster arrays reveal two plasmon peaks, shifted to higher and lower energies with respect to the one observed for alumina-supported Ag clusters. The presence of two resonance peaks is explained by considerable electromagnetic coupling in the cluster ensemble.