Migration of di- and tri-interstitials in silicon

A comprehensive study on the migration of di- and tri-interstitials in silicon is performed using classical molecular dynamics simulations with the Stillinger-Weber potential. The initial di- and tri-interstitial configurations with the lowest formation energies are determined, and then, the defect migration is investigated for temperatures between 800 and 1600 K. The defect diffusivity and the self-diffusion coefficient per defect are calculated. Compared to the mono-interstitial, the di-interstitial migrates faster, whereas the tri-interstitial diffuses slower. The migration mechanism of the di-interstitial shows a pronounced dependence on the temperature. Like in the case of the mono-interstitial, the mobility of the di-interstitial is higher than the mobility of the lattice atoms during the defect diffusion. On the other hand, the tri-interstitial mobility is lower than the corresponding atomic mobility. The implications of the present results for the analysis of experimental data on defect evolution and migration are discussed.