NRA and ERDA Investigation of Helium Retention in SiC as a Function of Irradiation and Annealing

Silicon carbide has been proposed for coating applications in advanced reactor designs, so studies of its behavior in the presence of ion irradiation and fission products are of Interest. We investigated the retention of He in single crystal 6H SiC as a function of irradiation dose and annealing temperature using both nuclear reaction analysis (NRA) and time-of-flight elastic recoil detection analysis (ToF ERDA). Ions of 3He+ were implanted at 40 keV in SiC to a depth of ∼200 nm at room temperature. NRA was performed using 1.0 MeV Dp+ and the 3He(D,α)1H reaction. No change in the He profile was seen for irradiation dose up to 6.8 x 1017 D+/cm2 at room temperature. Isochronal annealing of the SiC between 300 and 1200 K also showed no significant helium loss. Subsequently, a sample was irradiated with D+ at 900 K and again at 1100 K. No loss of 3He associated with irradiation was seen for a dose up to 5 x 1017 D+/cm2. Annealing the sample above 1200 K resulted in thermally activated loss of He. ToF ERDA measurements were performed using 44 MeV 127I10+ for both irradiation and analysis. Depth profiles of the He distribution showed no significant change under I bombardment with an ion fluence up to ∼1014/cm2 at room temperature. NRA was performed on the implanted sample subjected to ERDA. The 3He profiles for regions subjected to I irradiation were similar in shape to those with no I irradiation