Charge profile of surface doped C-60

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 mea n-field approximation. At low doping, the charge profile behaves similarly to the case of a continuous space-charge layer and becomes confined to a si ngle interface layer for doping higher than similar to0.3 electron (or hole ) per C-60 molecule. The morahedral disorder of the C-60 molecules smoothen s the structure in the density of states.