Because diffusion related phenomena become increasingly important as semiconductor device dimensions decrease, diffusion in Si has been heavily studied. The study of stress effects on diffusion is important, e.g., in the study of the stability for strained-layer epitaxial materials in semiconductor technology.

For studying the effect of hydrostatic pressure, we used molecular dynamic simulations with the modified Stillinger-Weber potential. The investigations of defect migration have been performed for a simulation cell, containing one <110> dumbbell interstitial or one di-interstitial with low formation energy.

The simulations for all interstitial configurations were performed at different temperatures and different hydrostatic pressures (zero, high and low). Fitting the data for the self-diffusion coefficient obtained in the simulations for mono-interstitial at zero pressure to the Arrhenius relation yields the values 0.012 cm²/s and 0.82 eV for the pre-exponential factor and barrier energy, respectively. These values are in reasonable agreement with the values 0.019 and 0.98 from [1], where MD simulations with the same empirical potential have been performed. The values obtained at zero pressure for di-interstitial are 2.3∙10^-4 (pre-exponential factor) and 0.54 eV (barrier energy). 

The dependence of the resulting diffusion coefficients on pressure has been analyzed and discussed. We can conclude that the self-diffusion coefficients decrease at higher pressure and increase at low pressure for both mono- and di-interstitials. The results have been compared with literature values for the pressure effect on diffusion, and the resulting agreements and disagreements are discussed critically.

[1] Posselt M., Gao F., Zwicker D. Atomistic study of the migration of di- and tri-interstitials in silicon // Phys. Rev. B – 2005. – V. 71 – P. 245202 – 245217.

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1. Quantumchemical Simulation of Growth and Structural Stability of Silicon Nanotubes