The diffusion of Cu through 100nm-thick Co films was investigated, using X-ray photoelectron spectroscopy, at temperatures ranging from 300 to 400C. The grain boundary diffusivities were determined by modelling the accumulation of Cu on Co surfaces as a function of time at a given temperature. It was found that the grain boundary diffusivity of Cu through Co could be described by:

D (cm2/s) = 2 x 104exp[-2.4(eV)/kT]

J.G.Pellerin, S.G.H.Anderson, P.S.Ho, C.Wooten, K.R.Coffey, J.K.Howard, K.Barmak: Journal of Applied Physics, 1994, 75[10], 5052-60