The intercalation of metal M (M = Au, Ag, In) from the electrode into the polycrystalline C60 and C70 thin films was studied by time-dependent and space-resolved conductivity measurements under controlled oxygen-free atmosphere at different temperatures and electric fields. The time resistivity behavior was interpreted on the basis of electric-field-induced diffusion of metal ions from the electrodes to the interstitials of the fullerene crystal lattice and local formation of MxC60 and MxC70 phases. A comparison between the resistivity behaviors of C60 and C70 thin films provides evidence that the process was sensitive to the electronic level structure of the fullerenes molecules.

Field-Induced Diffusion of Gold and Related Phase Transformations in the C60 and C70 Fullerenes. Firlej, L., Kirova, N., Zahab, A.: Physical Review B, 1999, 59[24], 16028-32