Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 66: Nanotribology I

O 66.7: Vortrag

Donnerstag, 25. März 2010, 12:00–12:15, H36

Atomic stick-slip friction on a metal vs. a monolayer lubri- cant surface. — •Nitya Nand Gosvami, Philip Egberts, and Roland Bennewitz — INM-Leibniz Institut für Neue Materialien, Saarbrücken, Germany

We study friction at the atomic scale on a Au(111) surface with and without an alkanethiol self-assembled monolayer (SAM) coverage. The experiments were performed using an atomic force microscope (AFM), operated in ultra-high vacuum (UHV) conditions. On atomically flat terraces of Au(111), very low friction with clear atomic stick-slip instabilities was observed which did not vary with load in the low load regime. However, as the normal load was increased beyond a threshold, friction showed sharp rise with significant variation in magnitude and accompanied with irregular stick-slip events, indicating wear of the surface. The striking observation of atomic stick-slip without dissipation can not be explained using existing classical models for single asperity friction. Our results also did not show agreement with a recently developed two-mass-two-spring model, which incorporates thermal effects. Alternate mechanisms for the observed friction behaviour are discussed.

We extended atomic scale friction studies to a SAM covered Au(111)surface. We found that the self-assembled molecules support atomic stick-slip friction where friction maps revealed the molecular superstructure of the SAM film. In several cases, frictional contrast down to single molecular level was achieved near the pull-off force.