Measurements were made of the diffusion coefficient of Ni in unrelaxed amorphous material, at temperatures between 270 and 435C, by means of secondary ion mass spectrometry. The data (table 72) could be described by:

D(cm2/s) = 3 x 10-3exp[-1.30(eV)/kT]

These values were some 6 to 8 orders of magnitude lower than that for the interstitial diffusion of Ni in crystalline Si. The diffusion process in amorphous material could be described by a model which invoked trap-retarded interstitial migration. The difference between the diffusion coefficients in amorphous and crystalline material was attributed mainly to the presence of intrinsic traps in the amorphous phase; with a binding enthalpy of about 0.83eV. Moreover, the experimental data indicated a lower attempt frequency for trapped Ni atoms than for free interstitial Ni.

Nickel Atomic Diffusion in Amorphous Silicon. A.J.Kuznetsov, B.G.Svensson: Applied Physics Letters, 1995, 66[17], 2229-30