A new technique was developed to study interdiffusion between two miscible metals. The technique was applied to the Ni–Pd system. It consists in measuring the change of apparent surface composition of a Pd substrate coated with an 800 nm Ni thin film during annealing at a given temperature. The measurement was carried out in-situ inside the chamber of a scanning electron microscope by EPMA–EDS (electron probe microanalysis–energy dispersive X-ray spectroscopy). The experimental data were processed using a model that mixes the Fick's diffusion equations and the electron probe microanalysis equation. This process allows the determination of the mean interdiffusion coefficient at a given annealing temperature. The main advantages of the technique were the possible determination of interdiffusion coefficients in thin films and at very low temperature (down to 430C, i.e. ~0.4Tm), which was not achievable with other techniques conventionally used for the study of interdiffusion. The Ni–Pd mean interdiffusion coefficient was shown to obey the Arrhenius law,

D(cm2/s) = 6.32 x 10-3exp[-178.8(kJ/mol)/RT]

between 430 and 900C, in relatively good agreement with previous interdiffusion measurements made of this system, but at higher temperatures.

EPMA–EDS Surface Measurements of Interdiffusion Coefficients between Miscible Metals in Thin Films. F.Christien, J.F.Pierson, A.Hassini, F.Capon, R.Le Gall, T.Brousse: Applied Surface Science, 2010, 256[6], 1855-60