Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 90: Methods: Scanning Probe Techniques II
O 90.7: Vortrag
Freitag, 29. Februar 2008, 11:45–12:00, MA 042
Experimental Observation of Amontonian und Superlubric Sliding in Extended Nanocontacts — •Dirk Dietzel1,2, Tristan Mönninghoff1, U. D. Schwarz3, Claudia Ritter3, Harald Fuchs1,2, and Andre Schirmeisen1 — 1Institute of Physics, University of Münster, Münster, Germany — 2INT, Forschungszentrum Karlsruhe (FZK), Karlsruhe, Germany — 3Department of Mechanical Engineering, Yale University, New Haven, CT, USA
One of the most fundamental questions in nanotribology is the contact area dependence of frictional forces on the nanometer scale. Unfortunately, conventional friction force microscopy techniques are limited for analyzing this problem due to the unknown and ill-defined tip-sample contact. This limitation can be circumvented by measuring the lateral force signal during the manipulation of nanoscale particles with a well-defined, clean contact to the substrate. In our study, the samples under investigation were metallic islands with diameters between 50-500 nm grown by thermal evaporation of antimony on highly oriented pyrolytic graphite (HOPG). Experiments that included the controlled manipulation of a large number of nanoparticles in ultrahigh vacuum show two distinct frictional states during particle sliding: While some particles show finite friction increasing linearly with interface area, thus reinforcing Amonton's law at the nanoscale, other particles assume a state of frictionless or 'superlubric' sliding. This unexpected duality of friction states can be explained by contamination effects of the interface that alter the frictional properties.