Studying the behavior of organic molecules adsorbed on graphene was an issue of special importance to exploit the full potential of graphene in future technology. A scanning tunnelling microscopy study in ultrahigh vacuum was made of the surface diffusion and initial stages of growth of a simple organic molecule, the azobenzene 1,3,5-triazine, on epitaxial graphene on Pt(111) at low temperatures. The study revealed the formation of fractal shape islands below 100K; inside the islands, the molecules were arranged in a well-ordered hexagonal structure with the molecular plane parallel to the surface. The orientation of the molecules in this lattice was determined by the interpretation of STM images exhibiting intramolecular features via the electrostatic potential map of the 1,3,5-triazine molecule. From nucleation experiments were measured, for the first time, the diffusion barrier for single molecules adsorbed on the graphene/Pt(111) surface. This energy barrier (68meV) was higher than that previously found for 1,3,5-triazine on graphite surfaces. This important finding showed that even on the graphene/Pt(111) system, which was one of the most weakly coupled graphene-metal systems, dynamic processes such as surface diffusion, which was a fundamental process involved in the growth of monolayers of organic molecules, was affected by the interaction of graphene with the underlying metal.

Surface Diffusion of Simple Organic Molecules on Graphene on Pt(111). Martínez-Galera, A.J., Gómez-Rodríguez, J.M.: Journal of Physical Chemistry C, 2011, 115[46], 23036-42