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

0574597 - FZÚ 2024 RIV US eng J - Journal Article
Liao, M. - Nicolini, Paolo - Polcar, T.
Separating anisotropic and isotropic friction between atomic force microscope tips and atomically flat surfaces.
Physical Review B. Roč. 107, č. 19 (2023), č. článku 195442. ISSN 2469-9950. E-ISSN 2469-9969
Research Infrastructure: e-INFRA CZ - 90140
Institutional support: RVO:68378271
Keywords : friction * layered crystals * surfaces * atomic force microscopy * materials modeling * condensed matter * Materials & Applied Physics
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 3.7, year: 2022
Method of publishing: Limited access
https://doi.org/10.1103/PhysRevB.107.195442

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.
Permanent Link: https://hdl.handle.net/11104/0346762