Comparison of Cavities Formed in Single Crystalline and Polycrystalline \alpha-SiC after H Implantation

Cavities and extended defects formed in single crystalline and polycrystalline \alpha-SiC implanted with H^+ ions are compared. The samples are investigated by cross-sectional transmission electron microscopy. H_2 bubbles are formed during H implantation and H_2 molecules escape the sample to form cavities during thermal annealing at 1100℃. Microcracks and the extended defects prefer to nucleate in single crystalline \alpha-SiC, but not polycrystalline \alpha-SiC. Grain boundaries can account for the experimental results. The formation of cavities on grain boundaries is investigated.