The growth of small faceted voids (vacancy clusters) was retarded because it required 2-dimensional nucleation at cluster facets. Vacancy agglomeration was markedly affected by the resultant time-lag in the production of larger voids. At low initial vacancy concentrations and/or high cooling rates, void formation was suppressed and the vacancies went mainly into clusters.

Nucleation and growth of faceted voids in silicon crystals V.V.Voronkov, R.Falster: Journal of Crystal Growth, 1999, 198-199[1-4], 399-403