On the mechanism of {111}-defect formation in silicon studied by in situ electron irradiation in a high resolution electron microscope

Abstract

The initial stages of point defect cluster formation on {111} habit planes in Si crystals have been investigated during in situ electron irradiation in a high resolution electron microscope to elucidate their nature and origin. It was observed that 〈110〉 interstitial chains located in {111} planes at regular spacing are formed by the agglomeration of self-interstitial atoms to the core of vacancy or interstitial Frank partial dislocation loops and by the insertion of interstitial chains between two perfect {111} planes. Based on experimental and calculated high resolution electron microscopy images a structural model for the {111}-defect is proposed which includes a regular sequence of double five-membered and single eight-membered rings in which no dangling bonds are involved. A dependence of the displacement vector of the {111}-defect on the formation mechanism is observed. An isolated {111}-defect is characterized by the fully relaxed atomic structure with a displacement vector of (a/5)〈111〉. The aggregation of self-interstitials in the core of Frank partial dislocations results in the relaxation of the strongly deformed crystal lattice by decreasing the displacement vector of initial defects.