On the correlation between resistivity changes and formation of germanium nuclei in AlGe alloys

The formation of germanium nuclei in a supersaturated AlGe alloy at temperatures below 140 °C has been observed by small angle X-ray scattering and resistivity changes. The latter have been analyzed quantitatively using the X-ray results. The resistivity decreases by (1) trapping of free, quenched-in vacancies by germanium atoms and by (2) reduction of the solute content and the vacancy concentration when nuclei form. Both solute atoms and vacancies are needed to form Ge nuclei since Ge has a larger atomic volume than the Al matrix. Simultaneously, the resistivity is increased proportional to the total interface area of these nuclei. This interpretation leads to reasonable parameters and confirms the internal consistency of the atomic model.