Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 9: Nanotribology
O 9.2: Talk
Monday, March 11, 2013, 10:45–11:00, H42
Superlubric sliding of metallic nanoparticles: The influence of contact area and orientation — •D. Dietzel1, M. Feldmann1, H. Fuchs2, U. D. Schwarz3, and A. Schirmeisen1 — 1Institute of Applied Physics, University of Giessen — 2Institute of Physics, University of Muenster — 3Yale University, New Haven, USA
Superlubricity, or also termed structural lubricity, is a fundamental concept where ultra-low friction between atomically flat surfaces can originate from the lattice mismatch at the interface. But while the basic principle is intriguingly simple, unambiguous experimental identification of structural lubricity is often problematic and can best be achieved by analyzing characteristic features unique to structural lubricity. Two of the most significant features are the distinct contact area dependence of friction and the dependence on relative orientation between nanoparticle and substrate: Theory predicts a decrease of shear stress with contact area and the existence of distinct orientations of pseudo-commensurability with sharp peaks in friction. To measure the interfacial friction we have manipulated metallic nanoparticles of different size on atomically flat surfaces by contact mode atomic force microscopy techniques. Our results confirm the sublinear scaling of friction with contact area. Moreover, we could identify different scaling for amorphous and crystalline particles in good agreement with theoretical predictions. In case of the crystalline Gold particles, we could also observe abrupt friction changes due to nanoparticle rotation. By measuring the relative orientation between particle and substrate such friction changes can be related to orientations of pseudo-commensurability.