Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 6: Tribology
O 6.3: Talk
Monday, March 7, 2016, 12:45–13:00, S053
Investingating the transition between stick-slip and smooth sliding with Intermodulation Friction Force Microscopy — •Per-Anders Thorén1, Astrid de Wijn2, Riccardo Borgani1, Daniel Forchheimer1, and David Haviland1 — 1Nanostructure Physics, Royal Institute of Technology, Stockholm, Sweden — 2Department of Physics, Stockholm University, Stockholm, Sweden
Friction is a complicated phenomenon involving nonlinear dynamics at different scales. The origin of friction is poorly understood, due in part to a lack of methods measuring the force acting on nanometer-scale asperities sliding at velocity of order cm/s. Dispite enormous advances in experimental technique this combination of small length scale and high velocity remained illusive. We present a technique for measuring the velocity-dependence of frictional forces on a single asperity (an AFM tip) reaching velocities up to several cm/s. The method is based on the measurement and analysis of intermodulation products, or frequency mixing of multiple drive tones near a high Q torsional resonance that arise from the nonlinear frictional force. The method gives the oscillation amplitude dependence of both conservative and dissipative dynamic force quadratures, revealing a transition between stick-slip and smooth sliding that is characteristic of friction at high speeds. We can explain the measurements with a modified Prandtl-Tomlinson model that accounts for the viscous and elastic nature of the asperity. With its high force sensitivity for small sliding amplitude, our method enables rapid and detailed surface mapping of the full velocity-dependence of frictional forces to sub 10 nm spatial resolution.