The migration of ion-implanted As in polycrystalline films (210 – 510nm) was studied, at between 750 and 950C, using Rutherford back-scattering methods. The form of the concentration profiles was determined by the combined effects of a low diffusivity in the bulk material and a higher diffusivity in the grain boundaries. The latter was independent of the concentration and was governed by an activation energy of 3.9eV. This was similar to the value for low As concentrations in single crystals. The results could be described by:

D(cm2/s) = 8.6 x 104exp[-3.9(eV)lkT]

These values were some four orders of magnitude higher than those for single crystals, while the diffusivity in the bulk of the grains was the same as that in single crystals.

Diffusion of Arsenic in Polycrystalline Silicon. B.Swaminathan, K.C.Saraswat, R.W.Dutton, T.I.Kamins: Applied Physics Letters, 1982, 40[9], 795-8