Diffusion and solubility of copper, silver, and gold in germanium

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Abstract
Diffusion profiles of Cu, Ag, and Au were recorded on Ge crystals with various dislocation densities using the spreading-resistance technique. The penetration rate of Cu in effectively highly dislocated samples proves to be much faster than in virtually dislocation-free material. In the case of intermediate dislocation densities, two-stage Cu profiles are found. Diffusion coefficients of Ag and Au do not depend on the presence of dislocations. For all three elements, equilibrium solubilities were taken from the boundary concentration of the penetration profiles. A combined analysis of diffusivity and solubility data reveals that all features can be explained within the framework of the dissociative mechanism involving interstitial-substitutional exchange with the aid of vacancies. Whereas transport of interstitial Cu atoms proceeds faster than that of vacancies, for Ag and Au the opposite case appears to be true.