Superlubricity of epitaxial monolayer WS2 on graphene

Abstract

We report on the superlubric sliding of monolayer tungsten disulfide (WS2) on epitaxial graphene (EG) on silicon carbide (SiC). WS2 single-crystalline flakes with lateral size of hundreds of nanometers are obtained via chemical vapor deposition (CVD) on EG and microscopic and diffraction analyses indicate that the WS2/EG stack is predominantly aligned with zero azimuthal rotation. Our experimental findings show that the WS2 flakes are prone to slide over graphene surfaces at room temperature when perturbed by a scanning probe microscopy (SPM) tip. Atomistic force field based molecular dynamics simulations indicate that through local physical deformation of the WS2 flake, the scanning tip releases enough energy to the flake to overcome the motion activation barrier and to trigger an ultra-low friction roto-translational displacement, that is superlubric. Experimental observations indicate that after the sliding, the WS2 flakes rest with a rotation of npi/3 with respect to graphene. Atomically resolved investigations show that the interface is atomically sharp and that the WS2 lattice is strain-free. These results help to shed light on nanotribological phenomena in van der Waals (vdW) heterostacks and suggest that the applicative potential of the WS2/graphene heterostructure can be extended by novel mechanical prospects.

arXiv comment27 pages, main text and supplementary information

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Cited by in corpus (6)

• Deterministic direct growth of WS2 on CVD graphene arrays
• Sliding friction and superlubricity of colloidal AFM probes coated by tribo-induced graphitic transfer layers
• Growth and applications of two-dimensional single crystals
• Local tuning of WS2 photoluminescence using polymeric micro-actuators in a monolithic van der Waals heterostructure
• Black Phosphorus n-type doping by Cu: a microscopic surface investigation
• Quantifying superlubricity of bilayer graphene from the mobility of interface dislocations