Résumé
The kinetics and reversibility of oxygen diffusion into the polycrystalline thin C
70 films have been studied by time dependent electrical conductivity measurements at different temperatures and at low probing electric fields (
E∼2 V
cm
−1). It has been shown that only the diffusion among film grains is reversible; the diffusion into voids of fullerene structure is much slower and in practice irreversible. Annealing of films in the air at
T>380 K leads to formation of a new semiconducting material (
E
a=1.5 eV) stable at ambient conditions. The oxygen diffusion into fcc C
70 crystal lattice has also been studied by computer calculations. A path of diffusion and diffusion coefficients have been found.
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