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O: Oberflächenphysik

O 23: Rastersondentechniken II

O 23.10: Vortrag

Dienstag, 9. März 2004, 18:00–18:15, H36

Manifestations of slow hysteretic atomic jumps in dynamic force microscopy — •R. Hoffmann^1,2, A. Baratoff¹, H.J. Hug¹ und H.-J. Güntherodt¹ — ¹Institut für Physik, Universität Basel, Klingelbergstr.82, CH-4056Basel, Schweiz — ²Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe

In dynamic force microscopy, the frequency shift and the excitation amplitude necessary to keep the cantilever oscillation at a constant amplitude can be measured simultaneously. The mechanisms leading to atomic-scale contrast in the excitation amplitude are currently the subject of controversies. Several authors suggested that the energy dissipated into hysteretic motion of atoms induced by the tip in every oscillation cycle could cause the observed effects [1]. Site-specific force-distance measurements[2] performed on KBr(001) provide insight into the relation between the excitation amplitude and the force. Below a certain critical tip-sample distance, the frequency jumps between two limiting curves on the time-scales of the order of seconds. The fact that these tip instabilities begin to occur at the same tip-sample distance as the energy dissipation suggests that the two are related.

[1] N. Sasaki and M. Tsukada, Jap. J. Appl. Phys. 39, L1334 (2000)

[2] M.A. Lantz et al., Science 291, 2580 (2001)