High-purity float-zone crystals with a secondary grown-in defect density of less than 102/cm2 were grown by using a critical V/G-value of 2 x 10-5cm2/sK, where V was the crystal growth rate and G was the axial temperature gradient at the crystal/melt interface. Because of the coexistence of self-interstitials and vacancies, the structure of grown-in defects was not clearly understood. In order to clarify the point defect reactions, electron irradiation in a high-resolution electron microscope at room temperature was used to study a so-called frozen clustering of both types of point defect. This depended upon the type of local point defect supersaturation in thin float-zone samples which were covered with Si3N4 films. It was shown that new types of extended defect were created via the isolated and combined clustering of vacancies and self-interstitial atoms on {113} and {111} habit planes. The existence of an energy barrier to the recombination of self-interstitials with extended vacancy aggregates resulted in the formation of unusual extended defects which had a displacement vector that was close to zero. It was proposed that the combined clustering of point defects on {113} could provoke the recombination of point defects at a higher temperature. However, the low energy of the {111} defect, and its highly ordered structure, suggested the possibility of such defect formation during vacancy-rich crystal growth.

FZ-Si Crystal Growth and HREM Study of New Types of Extended Defect During in situ Electron Irradiation. L.Fedina, A.Gutakovskii, A.Aseev: Journal of Crystal Growth, 2001, 229[1], 1-5