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O: Fachverband Oberflächenphysik
O 35: Poster Session - Tribology: Surfaces and Nanostructures
O 35.4: Poster
Montag, 16. März 2020, 18:15–20:00, P1C
Non-linear friction and load-induced hybridization on epitaxial graphene/SiC — •Bartosz Szczefanowicz1, Andreas Klemenz2, Michael Moseler2, and Roland Bennewitz1 — 1INM - Leibniz Insitute for New Materials, Saarbrücken, Germany — 2IWM - Fraunhofer Institute for Mechanics of Materials, Freiburg, Germany
Graphene as 2D material is tough in plane but exhibits weak interactions normal to the plane. These features result in excellent tribological properties such as ultralow friction, which was demonstrated by Atomic Force Microscopy (AFM) measurements on many different substrates. For epitaxial graphene grown on SiC(0001) [1], friction forces increase dramatically above a threshold in normal pressure [2]. We present experimental results recorded by AFM in ultrahigh vacuum for the velocity dependence of friction in the low and high pressure regime. Molecular dynamics simulations identify the pressure-induced local and intermittent hybridization of graphene with the underlying SiC(0001) substrate as origin of the friction increase. A similar rehybridization from sp2 to sp3 and creation of covalent bonds under the pressure of an AFM tip has been suggested to explain extraordinary stiffness results [3]. We discuss models to bridge the time gap between molecular dynamics simulations and AFM experiments, which lead to quantitative agreement.
[1] K.V. Emtsev et al., Nature Materials 8 (2009), 203 [2] T. Filleter and R. Bennewitz, Physical Review B, 81 (2010), 155412. [3] Y. Gao et al, Nature Nanotechnology, 13 (2018), 133.