Switchable friction enabled by nanoscale self-assembly on graphene

• Published in: Nature communications Vol. 7; no. 1; p. 10745
• Main Authors: Gallagher, Patrick, Lee, Menyoung, Amet, Francois, Maksymovych, Petro, Wang, Jun, Wang, Shuopei, Lu, Xiaobo, Zhang, Guangyu, Watanabe, Kenji, Taniguchi, Takashi, Goldhaber-Gordon, David
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23.02.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 142/126; 142/136; 639/301/923/966; 639/925/357/918; anisotropy; friction; graphine; Humanities and Social Sciences; MATERIALS SCIENCE; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms10745

Graphene monolayers are known to display domains of anisotropic friction with twofold symmetry and anisotropy exceeding 200%. This anisotropy has been thought to originate from periodic nanoscale ripples in the graphene sheet, which enhance puckering around a sliding asperity to a degree determined by the sliding direction. Here we demonstrate that these frictional domains derive not from structural features in the graphene but from self-assembly of environmental adsorbates into a highly regular superlattice of stripes with period 4–6 nm. The stripes and resulting frictional domains appear on monolayer and multilayer graphene on a variety of substrates, as well as on exfoliated flakes of hexagonal boron nitride. We show that the stripe-superlattices can be reproducibly and reversibly manipulated with submicrometre precision using a scanning probe microscope, allowing us to create arbitrary arrangements of frictional domains within a single flake. Our results suggest a revised understanding of the anisotropic friction observed on graphene and bulk graphite in terms of adsorbates. Graphene can exhibit pronounced frictional anisotropy, which was thought to arise because of nanoscale ripples. Here, the authors provide evidence that this effect could instead be a result of adsorbates that self-assemble into a highly regular superlattice of stripes with a period of four to six nanometres.