Amorphous multi-layers which had been prepared by sputtering were investigated by monitoring the enhancement of the first-order modulation peak during annealing at temperatures ranging from 473 to 523K. Effective interdiffusion coefficients which were as low as 10-25m2/s were measured. Negative true macroscopic interdiffusion coefficients were obtained by measuring the effective interdiffusion coefficient as a function of the modulation wavelength; thus indicating that there was a tendency to phase separation in the Co-C system. This was also predicted by a positive enthalpy of mixing which was calculated on the basis of Miedema’s macroscopic atom model. The true macroscopic interdiffusion coefficients could be described by:

D (m2/s) = 1.66 x 10-10exp[-128(kJ/mol)/RT]

The existence of a critical wavelength, below which the effective diffusion coefficient changed its sign, was proposed. It was calculated to be between 1.98 and 2.05nm at temperatures ranging from 473 to 523K.

H.L.Bai, E.Y.Jiang, C.D.Wang: Thin Solid Films, 1996, 286[1-2], 176-83