HREELS study of the intercalation of K atoms in C60 monolayers

Extra- and intramolecular vibrations of K-doped C₆₀ monolayers adsorbed on Ag(1 1 1) and Cu(1 1 1) have been studied by high-resolution electron energy loss spectroscopy (HREELS) in reflection geometry. Intramolecular modes are used to assess the electronic occupancy of C ₆₀, which is increased by intercalating K atoms. Regardless of the charge donated by the substrate, extramolecular modes have characteristic frequencies for K₁C₆₀, K₂C₆₀, and K₄C₆₀ monolayers. When the K concentration exceeds four, the K-doped monolayers exhibit different structures on Ag(1 1 1) and Cu(1 1 1).