Radiation exposure effect on deuterium retention in SiC

Abstract

Heavy ion (Fe³⁺) irradiation or gamma-ray irradiation of silicon carbide (β-SiC) was done to evaluate the radiation effect on hydrogen isotope retention in SiC. Thereafter, 1 keV D₂⁺ implantation or D₂ gas exposure was performed, and their D retentions were evaluated by thermal desorption spectroscopy (TDS). The D₂ TDS spectra consisted of two desorption stages, namely the desorption of D bound to Si as the Si-D bond and C as the C-D bond. The D retention for Fe³⁺ irradiated SiC at the lowest D₂⁺ fluence of 0.1 × 10²² D⁺ m^-2 was lower than that for unirradiated SiC. It was expected that the displaced C atoms would be accumulated near the surface region by Fe³⁺ irradiation, leading to their dynamic desorption in methane molecules. For gamma-ray irradiation, C or Si with dangling bonds were formed, which enhanced D trapping. It was concluded that the collision process caused during Fe³⁺ irradiation induced the dissociation of SiC matrix and C aggregates near the surface region, but the electron excitation by gamma-ray irradiation dissociated the single Si-C bond and the quick D trapping by dangling bonds enhanced D retention in SiC.