Separating anisotropic and isotropic friction between atomic force microscope tips and atomically flat surfaces

Layered materials are the most important class of solid lubricants. Friction on their surfaces has complex origins. Most experimental methods so far only give total friction force and cannot separate contributions from different origins. Here, we report a method to separate anisotropic and isotropic friction forces on atomically flat surfaces such as MoS2, graphite, h-BN, and mica by combining a two-dimensional friction force microscope technology and a two-dimensional friction model. We found that the friction force of most atomically flat surfaces is anisotropic, the total force on the tip misaligns with the scan direction, and the friction anisotropy vanishes under low sliding velocity. Our two-dimensional friction model explains experimental observations. It reveals the existence of elemental hopping combinations and the isotropic component in total friction. The misalignment angle can be used to calculate the ratio of anisotropic and isotropic friction components and the ratio of resistance forces from different lattice directions. The separation of anisotropic and isotropic friction forces will offer an avenue for studying the properties of individual friction components, which can boost the study of friction mechanisms in the future and benefit the application of solid lubricants.

10.1103/PhysRevB.107.195442

1550-235X

Liao, Mengzhou

e92e71bb-ebba-46b0-bcb8-819cb4f310cb

Nicolini, Paolo

80726840-4adf-44ea-a1dd-a77f9cb1e72d

Polcar, Tomas

c669b663-3ba9-4e7b-9f97-8ef5655ac6d2

Liao, Mengzhou

e92e71bb-ebba-46b0-bcb8-819cb4f310cb

Nicolini, Paolo

80726840-4adf-44ea-a1dd-a77f9cb1e72d

Polcar, Tomas

c669b663-3ba9-4e7b-9f97-8ef5655ac6d2

Liao, Mengzhou, Nicolini, Paolo and Polcar, Tomas (2023) Separating anisotropic and isotropic friction between atomic force microscope tips and atomically flat surfaces. Physical Review B, 107 (19), [195442]. (doi:10.1103/PhysRevB.107.195442).

Record type: Article

Abstract

Text

The friction anisotropy of 2D surfaces 2022.10.12 - Accepted Manuscript

Available under License University of Southampton Accepted Manuscript Licence.

Download (1MB)

More information

e-pub ahead of print date: 31 May 2023

Additional Information: Funding Information: M.L. acknowledges the support from ESI Fund, OPR DE International Mobility of Researchers MSCA-IF III at CTU in Prague (Grant No. CZ.02.2.69/0.0/0.0/20_079/0017983). M.L., P.N., and T.P. acknowledge support from the project Novel Nanostructures for Engineering Applications, Grant No. CZ.02.1.01/0.0/0.0/16_026/0008396. This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic through the e-INFRA CZ (Grant No. ID: 90140). TP acknowledges support from the European Union's Horizon2020 research and innovation program under grant agreement No. 721642: SOLUTION. Publisher Copyright: © 2023 American Physical Society.