Formation of a helium-bubble-free region in irradiated SiC via Mg ion implantation: Irradiation experiments combined with first-principles calculations

We unveiled the following findings: i) Mg implantation leads to the disappearance of 468 nm He bubbles in its vicinity, whereas He bubbles in Mg-free samples accumulate on the irradiated surface. The addition of Mg reduces the Raman peak shift induced by He irradiation, mitigating bond contraction. ii) The superiority of Mg lies in its ability to maintain the stability of SiC bonds and mechanical strength. He distorts and destabilizes the short-range lattice, causing neighbor instability. Atomic undercoordination by He and vacancy formation shorten the nearest Si–C bonds, leading to a dense electron and energy shell, which may contribute to irradiation-induced hardening. iii) The two abnormal density of states polarization peaks of He are attributed to neighbor instability and non-bonding states, while vacancies exhibit only polarization peaks. Mg does not alter the bandgap or Fermi level of SiC.