Self-Diffusion along Dislocations in Single-Crystal Au Films

Abstract

Self-diffusion measurements over the temperature range 247-352\ifmmode^\circ\else\textdegree\fi{}C have been made on single-crystal Au films of $2\ensuremath{-}\ensuremath{\mu}$ 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 \ifmmode\pm\else\textpm\fi{} 0.02 eV and 5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{4}$/sec, respectively. From the enhanced lattice diffusion observed in the first stage of the penetration profiles, a dislocation density of \ensuremath{\sim}${10}^{11}$ 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.