Diffusion and drift of a graphene flake on a graphite surface were analyzed. A potential energy relief of the graphene flake was computed using ab initio and empirical calculations. Based on the analysis of this relief, different mechanisms of diffusion and drift of the graphene flake on the graphite surface were considered. A new mechanism of diffusion and drift of the flake was proposed. According to the proposed mechanism, rotational transition of the flake from commensurate to incommensurate state takes place with subsequent simultaneous rotation and translational motion until a commensurate state was reached again, and so on. Analytic expressions for the diffusion coefficient and mobility of the flake corresponding to different mechanisms were derived in wide ranges of temperatures and sizes of the flake. The molecular dynamics simulations and estimates based on ab initio and empirical calculations demonstrated that the proposed mechanism could be dominant under certain conditions. The influence of structural defects on the diffusion of the flake was examined on the basis of calculations of the potential energy relief and molecular dynamics simulations. The methods of control over the diffusion and drift of graphene components in nano-electromechanical systems were discussed. The possibility to experimentally determine the barriers to relative motion of graphene layers based on the study of diffusion of a graphene flake was considered. The results obtained could also be applied to polycyclic aromatic molecules on graphene and should be qualitatively valid for a set of commensurate adsorbate-adsorbent systems.

Diffusion and Drift of Graphene Flake on Graphite Surface. Lebedeva, I.V., Knizhnik, A.A., Popov, A.M., Ershova, O.V., Lozovik, Y.E., Potapkin, B.V.: Journal of Chemical Physics, 2011, 134[10], 104505