Graphene is a unique 2D system of confined electrons with an unusual electronic structure of two inverted Dirac cones touching at a single point, having high electron mobility and promising microelectronics applications. The clean system had been studied extensively, but metal adsorption studies in controlled experiments were limited. Such experiments were important to the growth of uniform metallic films, metal contacts, carrier doping, etc. Two non-free-electron-like metals (rare earth Gd and transition metal Fe) were grown epitaxially onto graphene as a function of temperature T and coverage θ. By measuring the nucleated island density and its variation with growth conditions, information about the metal–graphene interaction (terrace diffusion, detachment energy) was extracted. The nucleated island densities at room temperature were stable and did not coarsen, at least up to 400C, which showed an unusually strong metal–graphene bond; most likely it was a result of C atom re-bonding from the pure graphene sp2 C–C configuration to one of lower energy.

Strong Metal Adatom–Substrate Interaction of Gd and Fe with Graphene. M.Hupalo, S.Binz, M.C.Tringides: Journal of Physics - Condensed Matter, 2011, 23[4], 045005