Silicon single crystals grown by the Czochralski process can contain various defects known as microdefects, formed by the agglomeration of vacancies and self-interstitials (or interstitials). The dynamics of the formation of interstitial-type microdefects is studied. Interstitials form globular clusters called B defects, which, upon sufficient growth, transform into the large dislocation loops known as A defects. A growing crystal exhibits a nucleation and growth zone, in which, at any given time, interstitials agglomerate to form B defects, B defects grow and transform into A defects, and A defects grow in size. The growth of the formed microdefects decreases the interstitial supersaturation and Suppresses the formation of new microdefects. By suddenly decreasing the temperature of the active nucleation and growth zone, the linear sizes of the relatively larger agglomerated A defects call be frozen, and smaller B and A defects ill higher densities call be formed, facilitated by a rapid increase in the interstitial supersaturation. The co-existence of both B and A defects was experimentally verified, and the width of the nucleation and growth zone was characterized. The quantification of the rapid-cooled nucleation and growth zone provides insights into the formation and the growth of the interstitial microdefects in particular and defect dynamics ill general. (c) 2005 Elsevier B.V. All rights reserved.