Strong metal adatom–substrate interaction of Gd and Fe with graphene

Abstract

Graphene is a unique 2D system of confined electrons with an unusual electronic structureof two inverted Dirac cones touching at a single point, with high electron mobilityand promising microelectronics applications. The clean system has been studiedextensively, but metal adsorption studies in controlled experiments have beenlimited; such experiments are important to grow uniform metallic films, metalcontacts, carrier doping, etc. Two non-free-electron-like metals (rare earth Gd andtransition metal Fe) were grown epitaxially on graphene as a function of temperatureT andcoverage θ. By measuring the nucleated island density and its variation with growth conditions, informationabout the metal–graphene interaction (terrace diffusion, detachment energy) is extracted. Thenucleated island densities at room temperature (RT) are stable and do not coarsen, at least up to400 °C, which shows an unusually strong metal–graphene bond; mostlikely it is a result of C atom rebonding from the pure graphenesp2 C–C configuration to one of lower energy.