It was recalled that He had a marked effect upon the microstructure of this material after implantation and subsequent annealing. A dense population of bubbles and dislocation loops was typically observed, for relatively low displacement doses, after annealing He-implanted α-phase samples, while no visible damage appeared after irradiation without He implantation. The defects were separated from the grain boundaries by defect-free zones which were about 0.5μm wide. The most interesting features were lenticular cavities which transformed into disk-shaped arrangements of bubbles with associated dislocation loops, stacks of loops. The observed microstructural changes, and their dependence upon implantation dose, annealing temperature and time were quantitatively explained in terms of the diffusion of interstitial He atoms and their clustering between adjacent lattice planes to form nano-cracks during implantation. Relaxation of the high gas pressure by matrix-atom transfer from bubbles to loops during annealing, and the coarsening of bubble-loop complexes, were described by a coupled 2-component Ostwald ripening process.

Microstructural Evolution of Helium-Implanted α-SiC J.Chen, P.Jung, H.Trinkaus: Physical Review B, 2000, 61[19], 12923-32