Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 33: Teilchen und Cluster II

O 33.7: Talk

Monday, March 7, 2005, 12:15–12:30, TU EB107

Dynamic force microscopy and spectroscopy investigations of Au₅₅ on Au(111) — •Georgeta Radu, Dirk Mautes, and Uwe Hartmann — Fachrichtung Experimentalphysik, Universität des Saarlandes, Postfach 151150, D-66041 Saarbrücken, Deutschland

Non-contact atomic force microscopy (NC-AFM) and spectroscopy were used to study thin films of ligand-stabilized Au₅₅ clusters deposited on Au(111). The clusters were dissolved in dichlormethane (CH₂Cl₂) and deposited onto a freshly prepared Au(111) substrate by spin coating. The deposit consist of a layer of single cluster height covering the Au(111) substrate. The NC-AFM images show many local areas where the clusters are arranged in a 2D closest packing alternating with areas showing the bare substrate. Frequency shift- and dissipation-versus-distance measurements on individual clusters as well as on the bare substrate were performed. The distance dependence of the interaction force was calculated from the experimental frequency-versus-distance curves for individual clusters as well as for the Au(111) substrate. On the basis of the results, a model of the tip-cluster and tip-substrate interaction force will be presented. Different distance dependencies of the dissipation curves taken on clusters and on the substrate were found. Dissipation mechanisms for the tip-cluster and tip-substrate interaction will be discussed.