title: Switchable friction enabled by nanoscale self-assembly on graphene.
abstract: 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.
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Gallagher
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Menyoung
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Physics, Duke University, Durham, North Carolina 27708, USA.|Department of Physics and Astronomy, Appalachian State University, Boone, North Carolina 28608, USA.
authors.forename: Francois
authors.initials: F
authors.lastname: Amet
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Petro
authors.initials: P
authors.lastname: Maksymovych
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Shuopei
authors.initials: S
authors.lastname: Wang
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Lu
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Zhang
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: David
authors.initials: D
authors.lastname: Goldhaber-Gordon