A thermodynamic approach to self-diffusion in silicon: Evidence of a single diffusion mechanism?

• Self-diffusion in Si is investigated in terms of the cBΩ thermodynamic model.
• The anharmonic behavior of bulk modulus explains the reported curved Arrhenius plot.
• The cBΩ model suggests the existence of a single diffusion mechanism.
• The activation enthalpy and entropy vary non-linearly with temperature.

The self-diffusion in silicon is investigated in terms of the cBΩ thermodynamic model, which connects point defect parameters with the bulk elastic and expansion properties. The curved Arrhenius plot of the recently reported experimental data on self-diffusion in Si by Kube et al. [Phys. Rev. B 88 (2013) 085206] and by Bracht [Physica B 376–377 (2006) 11] which is associated with two mechanisms (vacancies and self-interstitials) can be explained, if the non-linear anharmonic behavior of the isothermal bulk modulus is considered over the entire temperature range of the available experimental data. The latter suggests the existence of a single diffusion mechanism, in contrast to experimental evidence, which in the frame of the cBΩ model exhibits temperature dependent thermodynamic properties. Indeed, the calculated point defect parameters (activation enthalpy, activation entropy and activation Gibbs free energy) exhibit considerable temperature dependence, with the activation enthalpy varying in a non-linear way from 3.6 eV to 4.9 eV, in agreement with the interpretation of the aforementioned experimental data.