Blister formation and erosion due to blister fracture of SiC or Si

For silicon wafer and silicon carbide, helium ion irradiation followed by annealing was repeated, and the weight loss was measured. The blister formation and its fracture processes were also examined. For Si, many blisters were observed at the surface after the first ion irradiation. After the annealing at 1173 K after the irradiation, small pores formed by helium desorption were observed. With the increase of the cycle number, surface roughness gradually increased. The weight loss due to annealing was about a half of that by ion sputtering. The sputtering yield due to the ion irradiation was approximately twice the reference value in the present experiment, perhaps due to the bubble fracture during the irradiation. For SiC, small blisters were observed on SiC crystals after the ion irradiation. The erosion amount due to only the process of annealing at 1323 K was several times larger than that of ion sputtering, although the sputtering yield due to the ion irradiation was roughly the same as the reference value. The present erosion was significantly large, so that this erosion has to be taken into account regarding the wall lifetime and impurity level of the core plasma.