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

The initial stages pf 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.