講演番号をこちらに

06aC14
炭化珪素中にイオン注入された水素およびヘリウム挙動
Behavior of ion-implanted deuterium and helium in SiC
石川祐之助、永田晋二、四竈樹男
ISHIKAWA Yunosuke, NAGATA Shinji, SHIKAMA Tatsuo
東北大学工学研究科
School of Engineering, Tohoku University
Silicon carbide (SiC) is one of the most attractive candidates for components in fusion reactors such as thefirst wall, tritium breeding blankets, and insulating materials, owing to its inherent properties, such as lowactivation, good thermal conductivity, and stability at high temperatures. As a first wall material, SiC issubjected to severe condition with high-energy neutron and energetic helium (He) bombardment. Theseenvironment cause deterioration of the materials due to induced defects and introduced transmutation
products. In addition, in case of using SiC as insert between structural materials and tritium breeding
materials, the produced hydrogen isotopes, including tritium, are retained in the SiC and interact closely withHe. The retention of tritium in SiC is a critical issue from the viewpoint of the tritium breeding ratio.
Therefore, it is important to establish a fundamental understanding of the interactions between hydrogenisotopes and He. In this study, the retained concentration depth profiles of deuterium (D) and He in SiC weremeasured using ion beam analysis techniques to examine the influence of He pre-implantation on theretention/release behavior of D. The depth profiles of damaged Si sub-lattices were analyzed simultaneously
to elucidate the correlation between release behavior and damage recovery.
The samples used in this study were single crystal plates of α-SiC with <0001> orientation. 10 keV He+ andD2+ were implanted into the sample at an ion fluence of 1.0 × 1021 ions/m2 at room temperature (RT) and 770
K. The depth profiles of implanted D and He were measured by the elastic recoil detection (ERD) analysis
technique. To examine the correlation between D and He in the sample, 10 keV He+ ions were implanted into
the sample prior to the D ion implantation. After irradiation, the sample was annealed isochronally for 10min from RT up to 1370 K. Rutherford backscattering (RBS) analysis in a channeling condition was also
performed to calculate the amount of Si atoms displaced from the <0001> axis.
The depth profiling during isochronal annealing experiments showed that the D retention in He + implanted
sample at 1370 K was much smaller than that for D implanted into the non-irradiated sample. The reductionof D retention can be explained by He implantation-induced damage, which disturb the C–D bonds forming.
In addition, He release temperature
increased in the D2+ implanted sample asshown in Fig.1, which may be attributed tosuppression of He bubble formation by Dremaining in the sample at hightemperature. A correlation was not foundbetween the release behavior of implanted
ions by ERDA and the annealing behaviorof damage observed by RBS/C analysis
during the heat treatment. For implantation
at 770 K, the D retention andD-ion-induced disorder were decreased
considerably compared with 300 K
implantation, while the He retention andHe-ion-induced disorder did not change.

Fig.1. D and He retention as a function of annealing temperature