The time dependence of the decay of the dark electrical conductivity, σ(t), of C60 crystals under exposure to air was investigated at various temperatures. The decay of σ(t) could be fitted by using a stretched exponential function; indicating that the diffusion of O2 in C60 crystals followed a hierarchically constrained dynamic. The diffusivity of molecular O in C60 crystals was estimated by using the least-squares fitted time-constant. An activation energy of 1.5eV, corresponding to diffusion, was deduced from an Arrhenius plot of the data (table 1).

Diffusion of O2 in C60 Crystal by Measuring the Decay of Electrical Conductivity. C.M.Yang, J.L.Liao, K.C.Chiu: Journal of Applied Physics, 2004, 96[4], 1934-8

Table 1

Diffusivity of O in C60