Grown-in microdefects in dislocation-free silicon are distributed in banded patterns that result from a spatial variation in the type and concentration of the incorporated point defects: vacancies (at V/G larger than some critical value) or self-interstitials otherwise (V is the growth rate, G is the axial temperature gradient). The incorporated point defects agglomerate into microdefects upon lowering the temperature; particularly the vacancies are agglomerated into voids. Oxygen in Czochralski crystals plays an important role by assisting the void formation, by producing joint vacancy-oxygen agglomerates (oxide particles) and by trapping vacancies into VO2 Species. (C) 2007 Elsevier B.V. All rights reserved.