Native defects not only exhibit interesting physics of their own but also alter to a great extent the properties of materials. Many experimental and theoretical studies have been performed to understand the fundamental behavior and properties of self-interstitials in crystalline silicon. However, mechanisms underlying the evolution of extended defects starting from small clusters are still uncertain, despite their technological importance particularly in defining ultrashallow pn junctions for ever smaller semiconductor device fabrication. In this talk, we will present how small interstitial clusters evolve into rod-like {311} defects based on first-principles based atomistic modeling. Using combined density functional, tight binding molecular dynamics, and Metropolis Monte Carlo calculations, for the first time we have identified that deca-interstitials (I12) will serve as a key component for the growth of extended defects. We will show how the atomic configuration of interstitial defects changes with the size, together with their thermal stability. Our newly proposed model well predicts Ostwald ripening of interstitial clusters, consistent with experiment measurements available in literature. We will also compare our compact-to-extended transition model for interstitial defects with existing speculations.

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