Diffusion of O2 in C60 crystal by measuring the decay of electrical conductivity

The time dependence of the decay of dark electrical conductivity σ(t) from C60 crystals under air exposure was investigated at different temperatures. The decay of σ(t) can be fitted via a stretched exponential function, indicating that the diffusion of O2 in C60 crystal follows a hierarchically constrained dynamic. The diffusivity of molecular oxygen in C60 crystal is estimated using the least-square fitted time constant, and an activation energy EA=1.5eV corresponding to the diffusion process is deduced from the Arrhenius plot. The mechanism of the diffusion process is then discussed.