Charge transfer and structure in C60 adsorption on metal surfaces

The charge state and structure of C60 monolayers deposited on Au(110), polycrystalline Ag, and Ni(110) have been investigated by electron-energy-loss spectroscopy and low-energy electron diffraction. The vibrational excitation spectra have been used to obtain a quantitative determination of the molecular charge state of the adsorbed C60 molecules. On both the Au(110) and Ag surfaces the charge transfer from the surface to the C60 is found to be (1±1) electrons and that on Ni(110) is (2±1) electrons. These estimates are supported by the metallic nature of the low-energy (0–7.5 eV) electronic excitations of the monolayers. For submonolayer coverages of C60, rectangular overlayer phases are observed on Ni(110) in contrast to the close-packed islands seen on the other metals. This difference in the low-coverage structure can be related to differing substrate-adsorbate interactions, directly reflected by the C60 charge state.