Impurity Diffusion in Aluminum

Abstract

The diffusion of $^{71}\mathrm{Ge}$, $^{72}\mathrm{Ga}$, $^{65}\mathrm{Zn}$, $^{64}\mathrm{Cu}$, $^{110}\mathrm{Ag}$, and $^{198}\mathrm{Au}$ in aluminum single crystals has been measured by the tracer-sectioning technique. The diffusion coefficients, in ${\mathrm{cm}}^{2}$/sec, are given by: ${D}_{\mathrm{Ge}}=0.481\mathrm{exp}[\ensuremath{-}\frac{(28,980\ifmmode\pm\else\textpm\fi{}210)}{\mathrm{RT}}]$, ${D}_{\mathrm{Ga}}=0.490\mathrm{exp}[\ensuremath{-}\frac{(29,240\ifmmode\pm\else\textpm\fi{}141)}{\mathrm{RT}}]$, ${D}_{\mathrm{Zn}}=0.259\mathrm{exp}[\ensuremath{-}\frac{(28,860\ifmmode\pm\else\textpm\fi{}134)}{\mathrm{RT}}]$, ${D}_{\mathrm{Cu}}=0.647\mathrm{exp}[\ensuremath{-}\frac{(32,270\ifmmode\pm\else\textpm\fi{}270)}{\mathrm{RT}}]$, ${D}_{\mathrm{Ag}}=0.118\mathrm{exp}[\ensuremath{-}\frac{(27,830\ifmmode\pm\else\textpm\fi{}142)}{\mathrm{RT}}]$, and ${D}_{\mathrm{Au}}=0.131\mathrm{exp}[\ensuremath{-}\frac{(27,790\ifmmode\pm\else\textpm\fi{}240)}{\mathrm{RT}}]$. Less extensive measurements of the diffusion of $^{60}\mathrm{Co}$ and $^{51}\mathrm{Cr}$ in aluminum are also reported. The activation energies obtained in this study cannot be reconciled with the large impurity-vacancy binding energies deduced from quenching studies; the difference is explained in terms of clustering effects in the quenching experiments. The difference between the present data and the low values of ${D}_{0}$ and $Q$ for impurity diffusion in aluminum reported by Agarwala and co-workers can be explained by the effect of a surface oxide.