Impurity Diffusion in Aluminum

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: $D_{\mathrm{Ge}}=0.481\mathrm{}\exp [-\frac{(28,980\mathrm{}\pm 210)}{\mathrm{RT}}]$, $D_{\mathrm{Ga}}=0.490\mathrm{}\exp [-\frac{(29,240\mathrm{}\pm 141)}{\mathrm{RT}}]$, $D_{\mathrm{Zn}}=0.259\mathrm{}\exp [-\frac{(28,860\mathrm{}\pm 134)}{\mathrm{RT}}]$, $D_{\mathrm{Cu}}=0.647\mathrm{}\exp [-\frac{(32,270\mathrm{}\pm 270)}{\mathrm{RT}}]$, $D_{\mathrm{Ag}}=0.118\mathrm{}\exp [-\frac{(27,830\mathrm{}\pm 142)}{\mathrm{RT}}]$, and $D_{\mathrm{Au}}=0.131\mathrm{}\exp [-\frac{(27,790\mathrm{}\pm 240)}{\mathrm{RT}}]$. 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.