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.
| Original language | English |
|---|---|
| Article number | 10745 |
| Journal | Nature Communications |
| Volume | 7 |
| DOIs | |
| State | Published - Feb 23 2016 |
Funding
We gratefully acknowledge Byong-man Kim and Ryan Yoo of Park Systems for verifying the presence of stripes in our samples using their Park NX-10 AFM. We thank Daniel Wastl for carefully reading our manuscript and for encouraging us to re-examine whether the stripes we observed were caused by periodic structural ripples or self-assembled adsorbates. We thank Trevor Petach and Arthur Barnard for other helpful discussions. Sample fabrication and ambient AFM/STM were performed at the Stanford Nano Shared Facilities with support from the Air Force Office of Science Research, Award Number FA9550-12-1-02520. Variable-temperature AFM studies were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility; our use of the facility was supported by the Center for Probing the Nanoscale, an NSF NSEC, under grant PHY-0830228. S.W., X.L. and G.Z. acknowledge support from the National Basic Research Program of China (Program 973) under grant 2013CB934500, the National Natural Science Foundation of China under grants 61325021 and 91223204, and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences under grant XDB07010100. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT (Japan). T.T. acknowledges support from JSPS Grant-in-Aid for Scientific Research under grants 262480621 and 25106006.
| Funders | Funder number |
|---|---|
| DOE Office of Science | |
| NSF NSEC | PHY-0830228 |
| Directorate for Mathematical and Physical Sciences | 0830228 |
| Air Force Office of Scientific Research | FA9550-12-1-02520 |
| Japan Society for the Promotion of Science | 25106006, 262480621 |
| Ministry of Education, Culture, Sports, Science and Technology | |
| National Natural Science Foundation of China | 91223204, 61325021 |
| Chinese Academy of Sciences | XDB07010100 |
| National Basic Research Program of China (973 Program) | 2013CB934500 |