SADDLE-POINT CONFIGURATIONS FOR SELF-INTERSTITIAL MIGRATION IN SILICON

Reaction paths between low-energy configurations of a self-interstitia l in crystalline silicon are studied using two methods of sampling and analysis, one of which (the discretized path method) has not been pre viously applied to studying defect mobility. Given two minimum-energy defect configurations, a discretized path method is shown to provide a n efficient means of determining the saddle-point configuration along the reaction path. Conversely, for a known transition state configurat ion, eigenmode analysis enables one to find the stable configurations that are connected by the saddle. The results, obtained here using the Stillinger-Weber potential model, reveal two basic mechanisms of self -interstitial migration, a jump process involving the center of a dist ributed self-interstitial and a rotation of the defect configuration a bout this center. Since the lowest activation energy given by the pres ent saddle-point analysis corresponds to a transition that does not in volve the defect configuration of the lowest energy, it suggests that considering the formation and migration components of a defect activat ion energy separately can be misleading in identifying the dominant me chanism for mobility.