Frictional Characteristics of Atomically Thin Sheets

By Changgu Lee, Qunyang Li, William B. Kalb, Xin-Z Liu, H. Berger, Robert W. Carpick, James C. Hone. Science, 2010

1,676 citations recorded by the source corpus.

Thin Friction The rubbing motion between two surfaces is always hindered by friction, which is caused by continuous contacting and attraction between the surfaces. These interactions may only occur over a distance of a few nanometers, but what happens when the interacting materials are only that thick? Lee et al. (p. 76; see the Perspective by Müser and Shakhvorostov) explored the frictional properties of a silicon tip in contact with four atomically thin quasi–two dimensional materials with different electrical properties. For all the materials, the friction was seen to increase as the thickness of the film decreased, both for flakes supported by substrates and for regions placed above holes that formed freely suspended membranes. Placing graphene on mica, to which it strongly adheres, suppressed this trend. For these thin, weakly adhered films, out-of-plane buckling is likely to dominate the frictional response, which leads to this universal behavior. A universal trend is observed for the friction properties of thin films on weakly adhering substrates. Using friction force microscopy, we compared the nanoscale frictional characteristics of atomically thin sheets of graphene, molybdenum disulfide (MoS2), niobium diselenide, and hexagonal boron nitride exfoliated onto a weakly adherent substrate (silicon oxide) to those of their bulk counterparts. Measurements down to single atomic sheets revealed that friction monotonically increased as the number of layers decreased for all four materials. Suspended graphene membranes showed the same trend, but binding the graphene strongly to a mica surface suppressed the trend. Tip-sample adhesion forces were indistinguishable for all thicknesses and substrate arrangements. Both graphene and MoS2 exhibited atomic lattice stick-slip friction, with the thinnest sheets possessing a sliding-length–dependent increase in static friction. These observations, coupled with finite element modeling, suggest that the trend arises from the thinner sheets’ increased susceptibility to out-of-plane elastic deformation. The generality of the results indicates that this may be a universal characteristic of nanoscale friction for atomically thin materials weakly bound to substrates.

Subfields: Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/c4dfb39fb1c8b30dfe3abee7ab8d81378518ef4a

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In Atomic and Molecular Physics, and Optics

In Electrical and Electronic Engineering

In Materials Chemistry

Citations in the corpus

Nanotribological Properties of Fluorinated, Hydrogenated, and Oxidized Graphenes (2013, background): “Also, nanoscale friction has been used to identify the effect of anisotropic puckering on graphene [10, 13, 14].”