Observation of He bubbles in ion irradiated fusion materials by conductive atomic force microscopy

Using a non-destructive conductive atomic force microscope combined with the Ar+ etching technique, we demonstrate that nanoscale and conductive He bubbles are formed in the implanted layer of single-crystalline 6H-SiC irradiated with 100 keV He+. We find that the surface swelling of irradiated SiC samples is well correlated with the growth of elliptic He bubbles in the implanted layer. First-principle calculations are performed to estimate the internal pressure of the He bubble in the void of SiC. Analysis indicates that nanoscale He bubbles acting as a captor capture the He atoms diffusing along the implanted layer at an evaluated temperature and result in the surface swelling of irradiated SiC materials.