Vacancy effects on the formation of He and Kr cavities in 3C-SiC irradiated and annealed at elevated temperatures

Polycrystalline 3C-SiC was sequentially irradiated at 400 and 750 °C with 120 keV He2+ and 4 MeV Kr15+ ions to 1017 and 4 × 1016 cm−2, respectively. The Kr15+ ions penetrated the entire depth region of the He2+ ion implantation. Three areas of He2+, Kr15+ and He2+ + Kr15+ ion implanted SiC were created through masked overlapping irradiation. The sample was subsequently annealed at 1600 °C in vacuum and characterized using cross-sectional transmission electron microscopy and energy-dispersive X-ray spectroscopy. Compared to the He2+ ion only implanted SiC, He cavities show a smaller size and higher density in the co-implanted SiC. At 25 dpa, presence of He in the co-implanted 3C-SiC significantly promotes cavity growth; much smaller voids are formed in the Kr15+ ion only irradiated SiC at the same dose. In addition, local Kr migration and trapping at cavities occurs, but long-range Kr diffusion in SiC is not observed up to 1600 °C.