How Graphene Slides: Measurement and Theory of Strain-DependentFrictional Forces between Graphene and SiO2.

Strain,bending rigidity, and adhesion are interwoven in determininghow graphene responds when pulled across a substrate. Using Ramanspectroscopy of circular, graphene-sealed microchambers under variableexternal pressure, we demonstrate that graphene is not firmly anchoredto the substrate when pulled. Instead, as the suspended graphene ispushed into the chamber under pressure, the supported graphene outsidethe microchamber is stretched and slides, pulling in an annulus. AnalyzingRaman G band line scans with a continuum model extended to includesliding, we extract the pressure dependent sliding friction betweenthe SiO2substrate and mono-, bi-, and trilayer graphene.The sliding friction for trilayer graphene is directly proportionalto the applied load, but the friction for monolayer and bilayer grapheneis inversely proportional to the strain in the graphene, which isin violation of Amontons’ law. We attribute this behavior tothe high surface conformation enabled by the low bending rigidityand strong adhesion of few layer graphene. [ABSTRACT FROM AUTHOR]