Field-induced diffusion of gold and related phase transformations in the C-60 and C-70 fullerenes

The intercalation of metal M (M = Au, Ag, In) from the electrode into the p olycrystalline C-60 and C-70 thin films is studied by time-dependent and sp ace-resolved conductivity measurements under controlled oxygen-free atmosph ere at different temperatures and electric fields. The time resistivity beh avior is interpreted on the basis of electric-field-induced diffusion of me tal 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 C-60 and C-70 thin films provides evidence th at the process is sensitive to the electronic level structure of the fuller enes molecules. [S0163-1829(99)08823-2].