High-resolution electron microscopy of neutron-irradiation-induced dislocations in SiC

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Abstract
Neutron-irradiation-induced dislocations in β- and α-silicon carbide (SiC) were observed using a high-resolution electron microscope. In β-SiC, small planar defects about 20 nm in diameter lying on {111} planes were determined as interstitial Frank loops, having a Burgers vector b=⅓〈111〉. On the basis of image simulation by the multislice method, it was determined that the loops consist of an insertion of a single Si-C layer into {111} stacking to create two rotated layers. These loops were induced by heavy neutron irradiation doses of above approximately 5 × 1026 neutrons m−2 (E>0.1 MeV) in a fast reactor. Defect nuclei a few nanometres in diameter in hexagonal α-SiC were induced by lower doses in a thermal reactor (2 × 1025 neutrons m−2) (E > 0.1 MeV). They are on the (0001) basal plane and have a Burgers vector b=⅙[0001].