Frictional Behavior of Atomically Thin Sheets: Hexagonal-Shaped Graphene Islands Grown on Copper by Chemical Vapor Deposition

Abstract

Single asperity friction experiments using atomic force microscopy (AFM) have been conducted on chemical vapor deposited (CVD) graphene grown on polycrystalline copper foils. Graphene substantially lowers the friction force experienced by the sliding asperity of a silicon AFM tip compared to the surrounding oxidized copper surface by a factor ranging from 1.5 to 7 over loads from the adhesive minimum up to 80 nN. No damage to the graphene was observed over this range, showing that friction force microscopy serves as a facile, high contrast probe for identifying the presence of graphene on Cu. Consistent with studies of epitaxially grown, thermally grown, and mechanically exfoliated graphene films, the friction force measured between the tip and these CVD-prepared films depends on the number of layers of graphene present on the surface and reduces friction in comparison to the substrate. Friction results on graphene indicate that the layer-dependent friction properties result from puckering of the graphene sheet around the sliding tip. Substantial hysteresis in the normal force dependence of friction is observed with repeated scanning without breaking contact with a graphene-covered region. Because of the hysteresis, friction measured on graphene changes with time and maximum applied force, unless the tip slides over the edge of the graphene island or contact with the surface is broken. These results also indicate that relatively weak binding forces exist between the copper foil and these CVD-grown graphene sheets.

Friction of low-dimensional nanomaterial systems

“…This dependence on layer number is not limited only to mechanically exfoliated samples, but also applies to graphene prepared through chemical vapor deposition, as shown by Egberts et al [62]. They showed that the friction force of monolayer graphene is significantly larger than that of bilayer graphene deposited on copper foil and proved that layerdependent friction properties result from puckering of the graphene sheet around the sliding tip, consistent with the model proposed by Lee et al Furthermore, in the normal force as a function of friction, they observed a substantial hysteresis with repeated scanning without breaking contact with the graphenecovered region.…”

2D-nanomaterials for controlling friction and wear at interfaces

“…A recent study of CVD graphene grown on copper foil demonstrated a layer dependence of friction between bilayer and single layer graphene. The puckering effect was again observed and found to have a strong dependence on the normal force and sliding history with larger deformations observed at larger loads indicating a weak interaction with the underlying copper substrate [61]. In the case of CVD graphene grown on Ni (1 1 1), it was found that the graphene-Ni(1 1 1) interface has a strong interaction due to the covalent bonding character and is more rigid with respect to out-of-plane deformations with lower shear strength and work of adhesion compared to graphene on amorphous silica [57].…”

Synthesis, dispersion and lubrication potential of basal plane functionalized alkylated graphene nanosheets

“…[6][7][8] Recently, graphene has been explored as an excellent material for friction and wear reductions. [11][12][13][14][15][16][17] Besides the nanoscale frictional and adhesion properties, the micro and macro-tribological properties of graphene thin lms are gaining considerable interest owing to their potential for lubrication applications. 9 Kim et al demonstrated graphene as a thinnest solid lubricant that reduces the adhesion and friction forces between the contact surfaces on the nano-and micro-scale while protecting the coated surface.…”