Charge profile of surface doped C60

We study the charge profile of a C-60-FET (field effect transistor) as used in the experiments of Schon, Kloc and Batlogg. Using a tight-binding model, we calculate the charge profile treating the Coulomb interaction in a mean-field approximation. At low doping, the charge profile behaves similarly to the case of a continuous space-charge layer and becomes confined to a single interface layer for doping higher than similar to0.3 electron (or hole) per C-60 molecule. The morahedral disorder of the C-60 molecules smoothens the structure in the density of states.