Plasmon Excitation in 2D and 3D C₆₀ Studied by Photoemission

For near monolayer (ML) C₆₀ condensed on Sn substrate, x-ray photoemission studies of Cls level reveal a feature centered about 22eV below the main peak. Analyses show that the feature is caused by the plasmon loss of the two dimensional C₆₀ film. Bulk plasmon loss peak(～ 28 eV blow the main peak), which has been observed on thick C₆₀ films, was not observed on the C₆₀ films with coverage θ < 2 ML. It indicates that the 28eV energy loss feature is due to a bulk plasmon associated with the solid C₆₀ but not a single C₆₀ molecule.