Influence of helium on the nucleation and growth of bubbles in silicon: a multiscale modelling study

The formation and growth of helium-filled cavities in silicon have been investigated using both molecular dynamics simulations and rate equation cluster dynamics calculations. This multiscale approach allowed us to identify atomic scale mechanisms involved in nucleation and early growth steps, and to follow their dynamics over experimental timescales. We especially focus our analyses on the influence of helium. Our results first suggest that both Ostwald ripening and migration-coalescence mechanisms are jointly activated during bubble growth. We also discover that an original mechanism, based on the splitting of bubbles, could have a significant contribution. Overall, helium atoms are found to delay growth, proportionally to their concentration. This can be clearly observed at the nanosecond timescale. However, for longer timescales, cluster dynamics calculations also reveal periods of accelerated growth for specific helium concentrations. Finally, it is determined that the main effect of Si interstitials is to impede bubble growth, due to an early recombination with vacancies.