Impurity Diffusion in Aluminum

The diffusion of ⁷¹Ge, ⁷²Ga, ⁶⁵Zn, ⁶⁴Cu, ¹¹⁰Ag, and ¹⁹⁸Au in aluminum single crystals has been measured by the tracer-sectioning technique. The diffusion coefficients, in cm²/sec, are given by: DGe=0.481exp[-(28,980±210)RT], DGa=0.490exp[-(29,240±141)RT], DZn=0.259exp[-(28,860±134)RT], DCu=0.647exp[-(32,270±270)RT], DAg=0.118exp[-(27,830±142)RT], and DAu=0.131exp[-(27,790±240)RT]. Less extensive measurements of the diffusion of ⁶⁰Co and ⁵¹Cr 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 D₀ and Q for impurity diffusion in aluminum reported by Agarwala and co-workers can be explained by the effect of a surface oxide.