Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 59: Poster Session III (Nanotribology; Polymeric biomolecular films; Organic electronics and photovoltaics, Covalent networks on surfaces; Phase transitions; Particles and clusters; Transparent conductive oxides)
O 59.2: Poster
Mittwoch, 16. März 2011, 17:30–21:00, P3
Transition from Static to Kinetic Friction of Nanoparticles — •Michael Feldmann1, Dirk Dietzel1, Udo D. Schwarz2, and André Schirmeisen1 — 1Institute of Physics and Center for Nanotechnology, University of Münster, Germany — 2Department of Mechanical Engineering, Yale University, New Haven, USA
On macroscopic scales a phenomenological difference between static and sliding friction forces is routinely observed for contacts between solid surfaces. But does this hold true for nanoscopic contacts as well? We investigated this fundamental question through manipulation of thermally evaporated antimony nanoparticles over atomically flat HOPG substrates with the tip of a friction force microscope (FFM) [1]. In contrast to direct measurements with the FFM tip the manipulation of nanoparticles has important advantages of providing very well defined contact areas as well as enabling the precise measurement of static friction. A novel approach to nanoparticle manipulation, called 'tip-on-top' technique, allowed us to vary the lateral forces exerted on individually chosen particles in very small increments. This was achieved by scanning the FFM tip on top of the particle while slowly increasing the applied normal force. The results clearly show a transition between frictional states, corresponding to static and sliding friction. Interestingly, we observe a hysteresis when switching from the static friction to the sliding friction regime and back. We found that the ratio between the static and kinetic friction forces for individual particles is 1/2 independent of their size, in agreement with theoretical predictions. [1] Dietzel et al., Appl. Phys. Lett. 95, 53104 (2009)