A method was proposed for experimentally distinguishing impurity bulk diffusion from surface crossing by the systematic study of diffusion in bulk samples of varying dimensions: a varying thickness in the case of plane-parallel plates and a varying radius for spheres and long cylinders.

Discerning between Bulk Diffusion and Surface Crossing in Diffusion Measurements. Z.Burshtein, M.Sinder: Journal of Applied Physics, 2005, 97[3], 033503 (5pp)