Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 34: Rastersondentechniken II
O 34.1: Vortrag
Montag, 7. März 2005, 10:45–11:00, TU EB407
Investigation of the statistics of stick-slip friction on graphite — •Lars Jansen1,2, André Schirmeisen1,2, and Harald Fuchs1,2 — 1Physikalisches Institut, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Str. 10, 48149 Münster — 2CeNTech, Center for Nanotechnology, Gievenbecker Weg 11, 48149 Münster
The stick-slip mechanism is believed to be one fundamental process of atomic friction. It is described by the Tomlinson model for zero temperature [1]. In this model a tip jumps between two equilibrium positions of a surface potential. The lateral forces, inducing the jump are called jump heights. For finite temperatures these jump heights follow a statistical distribution due to thermal excitation [2]. We measured stick-slip friction on the atomic scale with an AFM and we will introduce a new analysis method to extract the statistical information i.e. the corresponding jump height histograms from the experimental data, acquired with a Si-tip on a vacuum cleaved HOPG surface under ultra high vacuum conditions. These histograms are in good quantitative agreement with the theoretical model [3]. From the histograms we can extract quantitative values for the effective energy barrier. We find that the energy barrier depends strongly on the exact position of the tip within the surface potential. As a result of this the theoretical model has to be expanded to two dimensions. Furthermore we can confirm that the histogram shape depends sensitively on the measurement parameters like scan speed and normal load, as predicted by the theory. [1] Tomlinson, Phil. Mag. 7 (1929), [2] Gnecco et al., PRL 84 (2000), [3] Sang et al., PRL. 84 (2001)