EFFECTS OF ANNEALING ON THE CONDUCTIVITY OF C-60 THIN-FILMS

Films of C-60, at different stages of annealing of T-c = 200 degrees a nd 300 degrees C have been electrical characterized over the temperatu re domain from -130 degrees C to T-c. X-ray diffraction revealed a ran dom polycrystalline fee structure with stacking defects of an intrinsi c nature, due to deposition conditions. The value of room-temperature conductivity was found to be in the range (6.3-1.0)10(-10) (Omega cm) (-1). In the stable annealed state the conductivity showed an activate d temperature dependence above 423 K and a non-activated dependence be low 330-280 K. The activation energies E(2) 0.8 eV (film thickness 0.7 0 mu m) and E(2) = 1.0 eV (film thickness 2.40 mu m) were in good agre ement with the energy gap values (1.63 eV and 2.08 eV) which were dedu ced from the al;sorption spectral dependence. Annealing decreased the non-activated contribution to conduction, extending the intrinsic cond uction temperature range.