The mechanism of {113} defect formation in silicon: clustering of interstitial-vacancy pairs studied by in situ high-resolution electron microscope irradiation.

We report the direct visualization of point defect clustering in {113} planes of silicon crystal using a transmission electron microscope, which was supported by structural modeling and high-resolution electron microscope image simulations. In the initial stage an accumulation of nonbonded interstitial-vacancy (I-V) pairs stacked at a distance of 7.68 Å along neighboring atomic chains located on the {113} plane takes place. Further broadening of the {113} defect across its plane is due to the formation of planar fourfold coordinated defects (FFCDs) perpendicular to chains accumulating I-V pairs. Closely packed FFCDs create a sequence of eightfold rings in the {113} plane, providing sites for additional interstitials. As a result, the perfect interstitial chains are built on the {113} plane to create an equilibrium structure. Self-ordering of point defects driven by their nonisotropic strain fields is assumed to be the main force for point defect clustering in the {113} plane under the existence of an energy barrier for their recombination.