A computational analysis of graphene adhesion on amorphous silica

摘要

We present a computational analysis of the morphology and adhesion energy of graphene on the surface of amorphous silica (a-SiO_2). The a-SiO_2 model surfaces obtained from the continuous random network model-based Metropolis Monte Carlo approach show Gaussian-like height distributions with an average standard deviation of 2.91 ± 0.56 A, in good agreement with existing experimental measurements (1.68-3.7 A). Our calculations clearly demonstrate that the optimal adhesion between graphene and a-SiO_2 occurs when the graphene sheet is slightly less corrugated than the underlying a-SiO_2 surface. From morphology analysis based on fast Fourier transform, we find that graphene may not conform well to the relatively small jagged features of the a-SiO_2 surface with wave lengths of smaller than 2nm, although it generally exhibits high-fidelity conformation to a-SiO_2 topographic features. For 18 independent samples, on average the van der Waals interaction at the graphene/a-SiO_2 interface is predicted to vary from E_(vdW) = 0.93 eV to 1.56 eV per unit cross-sectional area (nm~2 ) of the a-SiO_2 slab, depending on the choice of 12-6 Lennard-Jones potential parameters, while the predicted strain energy of corrugated graphene on a-SiO_2 is E_(st) - 0.25-0.36 eVm~2. The calculation results yield the graphene/a-SiO_2 adhesion energy of about E_(ad) - 0.7-1.2 eVm, given E_(ad) = E_(vdW)-E_(st). We also discuss how the adhesive strength is affected by the morphological conformity between the graphene sheet and the a-SiO_2 surface.