Superlubricity of epitaxial monolayer WS2 on graphene

作     者：Holger Buch Antonio Rossi Stiven Forti Domenica Convertino Valentina Tozzini Camilla Coletti 

作者机构：Center for Nanotechnology Innovation @NEST Istituto Italiano di Tecnologia Piazza S. Silvestro 12 56127 Pisa Italy NEST Istituto Nanoscienze - CNR and Scuola Normale Supefiore Piazza San Silvestro 12 56127 Pisa Italy Graphene Labs Istituto Italiano di Tecnologia Via Morego 30 16163 Genova Italy 

出 版 物：《Nano Research》 (纳米研究（英文版）)

年 卷 期：2018年第11卷第11期

页      面：5946-5956页

核心收录：

学科分类：07[理学] 

基　　金：The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement 

主　　题：superlubricity graphene tungsten disulfide scanning tunneling microscopy (STM) two-dimensional (2D) materials nanomechanical 

摘      要：We report the superlubric sliding of monolayer tungsten disulfide (WS2) on epitaxial graphene (EG) grown on silicon carbide (SiC). Single-crystalline WS2 flakes with lateral size of hundreds of nanometers are obtained via chemical vapor deposition (CVD) on EG. Microscopic and diffraction analyses indicate that the WS2/EG stack is predominantly aligned with zero azimuthal rotation. The present experiments show that, when perturbed by a scanning probe microscopy (SPM) tip, the WS2 flakes are prone to slide over the graphene surfaces at room temperature. 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 trigger an ultralow-friction rototranslational displacement, that is superlubric. Experimental observations show that, after sliding, the WS2 flakes come to rest with a rotation of nπ/3 with respect to graphene. Moreover, atomically resolved measurements show that the interface is atomically sharp and 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.