A comparison of defects in helium implanted α- and β-SiC

Specimens of α- and β-SiC were implanted homogeneously at room temperature with helium to about 30% of their thickness to concentrations up to 2450 atppm. Lattice straining was determined from the bending radius of the specimens by surface profilometry after implantation and during subsequent annealing. Evolution and annealing of straining in α- and β-SiC were remarkably similar. Above 1300°C specimen volume increased, which, according to transmission electron microscopy, was ascribed to the growth of helium clusters. Microstructural investigations showed bubbles along grain boundaries and disk-shaped clusters of bubbles in the grain interior on (0 0 0 1) habit planes in hexagonal α-SiC and on (1 1 1) in cubic β-SiC.