Anisotropic Frictional Response of Texture Induced Strained Graphene

TL;DR

This study investigates how strain induced by textured surfaces affects the anisotropic frictional response of graphene, revealing ultra-low and direction-dependent friction forces useful for nanoscale device applications.

Contribution

It demonstrates strain-controlled anisotropic friction modulation in graphene on textured surfaces, combining experimental and simulation approaches for the first time.

Findings

Graphene reduces friction by a factor of 10 on textured surfaces.

Ultra-low friction of 20 times lower is achieved along the groove axis.

Friction anisotropy depends on strain and surface geometry.

Abstract

Friction-induced energy dissipation impedes the performance of nanoscale devices during their relative motion. Nevertheless, an ingeniously designed structure which utilizes graphene topping can tune the friction force signal by inducing local strain. The present work reports capping of graphene over Si grooved surfaces of different pitch lengths from sub-nanoscale (P=40 nm) to a quarter of a micron (P= 250 nm). The variation in the pitch lengths induces different strains in graphene revealed by scanning probe techniques, Raman spectroscopy and molecular dynamics (MD) simulation. The asymmetric straining of C-C bonds over the groove architecture is exploited through friction force microscopy in different directions of orthogonal and parallel to groove axis. The presence of graphene lubricates the textured surface by a factor of 10 and periodically dissipated friction force, which was found to be stochastic over the bare surface. For the first time, we presented transformation of the lubrication into an ultra-low friction force by a factor of 20 over the crest scanning parallel to the groove axis. Such anisotropy is found to be insignificant at the bare textured system, clearly demonstrating the strain-dependent regulation of friction force. Our results are applicable for graphene, and other 2D materials covered corrugated structures with movable components such as NEMS, nanoscale gears and robotics.