Accumulation and recovery of irradiation damage in He+ implanted α-SiC

In situ RBS/channeling (RBS/C) has been used to investigate damage accumulation and subsequent annealing behavior in single-crystal wafers of 6H-silicon carbide (α-SiC) irradiated at temperatures from 160 to 300 K with 390 keV He+ ions to fluences ranging from 7.5 x 1018 to 1.0 x 1020 He+/m2. Damage recovery in the irradiated crystals was studied by isochronal annealing at temperatures up to 1170 K. The RBS/C results show that complete amorphization in α-SiC does not occur at 190 K for irradiation fluences up to 1.0 x 1020 He+/m2 (0.38 dpa at the damage peak). For a fluence of 4.5 x 1019 He+/m2, the relative amount of damage accumulated during irradiation at 190 K is a factor of 5 larger than that accumulated under irradiation at 300 K, which suggests a higher rate of simultaneous point defect recombination at 300 K. In post-irradiation isochronal annealing studies, the integrated damage profile for all irradiated samples decreased exponentially with increasing annealing temperature. At low relative ion fluences and comparable irradiation-induced defect concentrations, the defects produced by He+ irradiation at 160 K are more difficult to anneal at 300 K than those produced by Si+ irradiation at 160 K, which suggests that trapping of He atoms at defects may be inhibiting recombination. (orig.)