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Limited diffusion spaces which may be easily traversed by atoms diffusing along grain boundaries generally cause thin-film diffusion to differ from common bulk diffusion. These peculiarities were studied in Ag−Au thin-film couples by means of electrical resistance measurements. Diffusion coefficients were found to decrease with annealing time mainly as a consequence of recrystallisation and recovery in the films during the diffusion anneal. It is shown that the rate of homogenisation is fairly independent of the film thickness thus giving evidence that diffusion into the crystallites occurs out of the grain boundary network rather than directly through the couple interface. Effective diffusion coefficients determined between 150 and 250° C ranged from 10 to 10 cm s revealing an activation energy of 25 kcal mol. [ABSTRACT FROM AUTHOR]

Computer simulation of superimposed lattice, grain boundary and surface diffusion, characteristic for polycrystalline thin film diffusion systems, was performed by way of discretisation of the nonlinear diffusion law. In order to give a vivid impression how such a complex process takes place under some typical conditions we have chosen pseudo three-dimensional computer plots of the spacial distribution of the concentration instead of the commonly used iso-concentration diagrams. The following cases are considered: [ABSTRACT FROM AUTHOR]

An x-ray method for the determination of concentration profiles in thin film diffusion couples is presented. This method is based on the theory of Fourier analysis of x-ray diffraction profiles which is generalized to polycrystalline samples showing nonuniform lattice parameter. A Fourier synthesis of the concentration spectrum is possible when the influences of the particle size and the strain in the sample as well as the instrumental function are eliminated from the measured diffraction profile. This can be done by means of reference profiles obtained from layers of the diffusion components. Absorption of the radiation in the sample is negligible when diffusion couples of symmetrical sandwich structure are used. The method is tested experimentally in the system Au-Cu. [ABSTRACT FROM AUTHOR]

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