Electronic states of a C₇₀ monolayer on the surface of Ag(111)

We have investigated the electronic states of a C₇₀monolayer on the surface of Ag(111) (1ML C₇₀/Ag(111)) using synchrotron radiation photoelectron spectroscopy and soft x-ray absorption spectroscopy techniques. The experimental data exhibit metallic properties and at least 2.6e charge transfer per C₇₀ molecule. The screening effect of Ag(111) on the electronic structure of C₇₀ is remarkable; it greatly reduces or even eliminates the on-site Hubbard energy. The work functions of the C₇₀ multilayer and monolayer are determined as 4.53eV and 4.52eV respectively. The energy levels of C₇₀ align with the Fermi level of the Ag(111) substrate, and the shift of the vacuum level caused by C₇₀ adsorption is negligible. Potassium doping indicates that 1ML C₇₀/Ag(111) can still accommodate about nine electrons and that the sample remains metallic at any doping level.