It was noted that, since diffusion in solids was affected by trapping sites which had various binding energies, analytical solutions which described diffusion in the presence of several types of trapping site were derived for dilute systems; without making the assumption of local equilibrium. Numerical comparisons with the local equilibrium treatment showed that the transport of free atoms, as evaluated here, was faster at short times than that according to the local equilibrium treatment. The difference became small with the passing of time. The present solutions also showed that the transport of free atoms was influenced by the initial concentrations at trapping sites, and that the apparent transport was accelerated in some cases. By using the present solutions, the systematic investigation of diffusion phenomena involving many types of trapping site became possible.

Diffusion with Multiple Kinds of Trapping Sites T.Kasuya, M.Fuji: Journal of Applied Physics, 1998, 83[6], 3039-48