Temperature dependence of the conductivity and kinetics of oxygen intercalation of C70 films

Electrical conductivity values of 1.8x10(-9) to 1.8X10(-13) (Omega cm)(-1) at 30 degrees C were found in undoped C-70 films, and the conductivity is thermally activated with an activation energy of 0.51-0.81 eV and a preexponential factor of 0.5 (Omega cm)(-1). We demonstrated that the conductivity decay due to oxygen intercalation follows sigma(t)=sigma(0)t(-alpha), where alpha much less than 1 when 0<t<t1, alpha greater than or equal to 1 when t1<t<t2, and 0.5 less than or equal to alpha<1.0 when t>t2,corresponding to three processes of oxygen reaction with the film. [S0163-1829(98)01308-3].