Self-Diffusion along Dislocations in Single-Crystal Au Films

Self-diffusion measurements over the temperature range 247-352^∘{}C have been made on single-crystal Au films of 2-μ thickness grown epitaxially onto (001) MgO substrates, using Au¹⁹⁵ 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 Qd and the combined preexponential factor AdDd⁰ for self-diffusion along dislocations are found to be 1.16 ±{} 0.02 eV and 5 ×{} 10^-16 cm⁴/sec, respectively. From the enhanced lattice diffusion observed in the first stage of the penetration profiles, a dislocation density of {~}10¹¹ lines/cm² 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.