Auger depth profiling technique and X-ray diffraction analysis were used to study interdiffusion in vacuum-deposited Cu–Ni bilayer thin films. An adaptation of the Whipple model was used to determine the diffusion coefficients of Ni in Cu and of Cu in Ni. The calculated diffusion coefficient was given by:

D (cm2/s) = 2.0 x 10-7 exp[-1.0(eV)/kT]

for Ni in Cu, and by:

D (cm2/s) = 6 x 10-8 exp[-0.98(eV)/kT]

for Cu in Ni. The difference between the diffusion parameters obtained here, and those reported elsewhere, was attributed mainly to differences in the film microstructure and the annealing ambient. It was concluded that interdiffusion in the investigated films was described by type-B kinetics in which rapid grain-boundary diffusion was coupled to defect-enhanced diffusion into the grain interior. The effectiveness of Ni as a diffusion barrier between Cu and a Si substrate was thus deemed to be suspect.

Investigation of Interdiffusion in Copper–Nickel Bilayer Thin Films. A.M.Abdul-Lettif: Physica B, 2007, 388[1-2], 107-11