Self-diffusion of silicon in polycrystallinePd2Si in the absence of growth

The self-diffusion of silicon in polycrystalline ${\mathrm{Pd}}_2$Si has been investigated with the aid of radioactive ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$ over the temperature range 350–550 °C. The results show that silicon self-diffusion occurs by a combination of rapid grain-boundary diffusion and slower lattice diffusion. A model has been adopted that can reproduce the observed ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$ concentration profiles over the above-mentioned range. The coefficient for grain-boundary diffusion is found to be at least ${10}^5$ times larger than that for lattice diffusion. The grain boundaries thus effectively act as instantaneous sources, and the overall silicon self-diffusion is controlled by bulk lattice diffusion. Using the adopted model, the activation energy for bulk lattice diffusion has been determined to be 0.8±0.1 eV.