Surface composition of K3C60 multilayers and C60 3 monolayers investigated by high-resolution electron energy loss spectroscopy

High-resolution electron energy loss spectroscopy (HREELS) in reflection geometry was used to probe the surface of K3C60 multilayer films as well as C60 3 monolayers adsorbed on Ag(1 1 1) and Cu(1 1 1). The 3 charge state of the adsorbed fullerenes was obtained by distilling K-saturated C60 monolayers.We found that roughly 2 electrons are donated by the K atoms on Ag(1 1 1) and slightly less than 1.5 electron in the case of Cu(1 1 1), the charge difference being provided by the metallic substrates. The surface of the K3C60 multilayer films has a charge state of about 1:5 and is thus underdoped