Studies of irradiation damage using a high voltage electron microscope

Abstract

A high voltage electron microscope was used to study loop formation in thin foils of pure and impure nickel. The effects of variation in flux, impurities and temperature were examined in the light of an existing theory for loop nucleation and growth. It was found that diffusion of point defects to the foil surfaces had to be taken into account for all quantitative work. The corrected volume densities of defect clusters produced at various temperatures between room temperature and about 500 K are in agreement with the theory and the results suggest that the migration energy of a free self-interstitial in nickel is (0.21 ± 0.05) eV and that its binding energy with a silicon atom is (0.26 ± 0.06) eV. At higher temperatures the experimental volume densities show considerable deviation from theoretical predictions, but this deviation has been shown to arise from the instability of di-interstitials. From the experimental data obtained at higher temperatures, the dissociation energy of a di-interstitial may be determined. This was found to be (0.8 ± 0.1) eV for nickel.