Morphology and Friction Characterization of CVD Grown Graphene on Polycrystalline Nickel

Nanoscale friction properties of graphene produced by Mechanical Exfoliation (ME) of graphite crystal and grown by CVD have been studied by Atomic Force Microscopy (AFM). In particular we have analyzed ME graphene deposited on SiO₂ (300 nm oxide) with respect to CVD graphene grown on polycrystalline Ni. We use the AFM in Friction Force Mode (FFM) with force resolution in the nano-newton range and lateral resolution in the nanometer scale. The detailed morphology of the samples, that may strongly influence the friction response at these length scales, has been analyzed by Raman spectroscopy and SEM imaging. We confirm that on ME graphene on SiO₂ friction force decreases film thickness (i.e. increasing the effective number of layers that compose the film). Moreover we verify that the same behavior appears for graphene grown by CVD on polycrystalline Ni substrate indicating that this characteristic is a specific mechanical properties of a few layer film.