Self-Diffusion along Dislocations in Single-Crystal Au Films

Abstract

Self-diffusion measurements over the temperature range 247-352°C have been made on single-crystal Au films of $2-\mu$ thickness grown epitaxially onto (001) MgO substrates, using ${\mathrm{Au}}^{195}$ radioactive tracer and rf sputter-etching techniques for serial sectioning. The penetration profiles revealed shallow lattice diffusion and a much deeper tracer penetration down dislocations; the former is significantly enhanced by diffusion in dislocations. The activation energy $Q_d$ and the combined preexponential factor $A_d{D}_d^0$ for self-diffusion along dislocations are found to be 1.16 ± 0.02 eV and 5 × ${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^4$/sec, respectively. From the enhanced lattice diffusion observed in the first stage of the penetration profiles, a dislocation density of ∼${10}^{11}$ lines/${\mathrm{cm}}^2$ could also be evaluated for the single-crystal films. The data compare well with other fcc metals and appear to favor a vacancy diffusion mechanism.