Effects of silicon and germanium adsorbed on graphene

Based on the first-principles plane wave calculations, we studied the adsorption of Si and Ge on graphene. We found that these atoms are bound to graphene at the bridge site with a significant binding energy, while many other atoms are bound at the hollow site above the center of hexagon. It is remarkable that these adatoms may induce important changes in the electronic structure of graphene even at low coverage. Semimetallic graphene becomes metallized and attains a magnetic moment. The combination of adatom orbitals with those of pi- and pi(*)-states of bare graphene is found responsible for these effects.