FIELD-INDUCED METAL DIFFUSION INTO C-60 THIN-FILMS

We report the evolution in time of d.c. conductivity of polycrystallin e thin films of C-60 at different temperatures and under various appli ed voltages. All films show a clear semiconducting behaviour. The init ial resistivity (at T = 140 degrees C) and the activation energy are r ho similar to 10(5) Ohm cm and E(a) similar to 0.5 eV, respectively. F or various types of metallic electrodes M (M = Au, Ag or In), a field- induced conductivity increase by several orders of magnitude and an ac tivation energy decrease are observed. The results are interpreted in terms of electrode metal diffusion into the film.