Development of the electronic structure in a K-doped C-60 monolayer on a Ag(111) surface

We present an electron spectroscopy study of the development of the electronic structure in the K-doped C-60 monolayer on a Ag(1 1 1) surface. We find that the occupation of the lowest unoccupied molecular orbital (LUMO) of the C-60 can be varied continuously from 0.75 (undoped) to 6.0 (fully doped). We also find that the density of states at the Fermi level for a doping level corresponding to 3 electrons per C-60 is at least a factor of two higher than that found from photoemission on bulk K3C60. This enhanced density of states at the Fermi level might suggest an increased superconducting transition temperature for the monolayer system. (C) 1997 Elsevier Science Ltd.