The kinetics and reversibility of oxygen diffusion into the polycrystalline thin C70 films were studied by time dependent electrical conductivity measurements at different temperatures and at low probing electric fields (E ∼ 2V/cm). It was shown that only the diffusion among film grains was reversible; the diffusion into voids of fullerene structure was much slower and in practice irreversible. Annealing of films in the air at T > 380K leads to formation of a new semiconducting material (Ea = 1.5eV) stable at ambient conditions. The oxygen diffusion into face-centered cubic C70 crystal lattice was also studied by computer calculations. A path of diffusion and diffusion coefficients were found.

Relationships between Crystallinity, Oxygen Diffusion and Electrical Conductivity of Evaporated C70 Thin Films. Fabiański, R., Firlej, L., Zahab, A., Kuchta, B.: Solid State Sciences, 2002, 4[8], 1009-15