Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 27: Scanning probe techniques II

O 27.5: Talk

Tuesday, March 28, 2006, 16:45–17:00, WIL B321

Investigation of dissipative interaction between probe and ligand-stabilized clusters by NC-AFM — •Georgeta Radu and Uwe Hartmann — Institute of Experimental Physics, Saarland University, P.O. Box 151150, D-66041 Saarbrücken, Germany

In recent years, noncontact atomic force microscopy (NC-AFM) became a powerful tool for imaging at high resolution as well as for probing specific surface properties. A major advantage of NC-AFM is the ability to distinguish between conservative and dissipative interactions. In order to investigate the dissipative interaction between the AFM probe and individual clusters, thin films of ligand-stabilized Au₅₅ clusters on an Au(111) substrate have been prepared. The NC-AFM images show locally ordered Au₅₅ monolayer islands with single cluster resolution. Dissipative interactions can be investigated by NC-AFM by measuring the damping of the cantilever oscillation as a function of the probe-sample distance. Damping-versus-distance measurements were performed on individual clusters as well as on the bare substrate. A distance dependence corresponding to the electric-field mediated Joule-dissipation [1] was found for the energy dissipated above individual clusters as well as on the bare substrate. No additional energy dissipation due to the mechanical deformation of the ligand shell under the action of the oscillating tip was observed. This is in agreement with the theoretical calculations by Couturier et al. [2].

[1] W. Denk and D. Pohl, Appl. Phys. Lett. 59, 2171 (1991)

[2] G. Couturier et al., J. Phys. D: Appl. Phys. 34, 1266 (2001)