Repelling effects of Mg on the diffusion of He atoms towards surface in SiC: Irradiation and annealing experiments combined with the first-principles calculations

In this study, the effects of Mg on the formation of He bubbles and diffusion behavior of He atoms in 3C-SiC were investigated by irradiation and annealing experiment as well as the first-principles calculations. TEM results indicated that two damage bands were formed in the He&Mg irradiated SiC. During annealing, Mg could prevent He atoms from diffusing to the surface, resulting in the formation of He bubbles in the deeper areas far from the Mg-implanted regions, which is helpful to avoid the surface blisters. First-principles calculations were then performed to explore the effects of Mg on the He behavior in SiC. The solution energy, binding energy charge density, bond length, and crystal orbital Hamiltonian population of these elements were calculated to identify their states. The results suggested that the binding capacity between He and Mg was weak, and Mg could increase the diffusion energy barrier of He. AIMD simulation showed that Mg could make He in a high-energy unstable state, and force He atom to move toward the vacancy away from Mg, which explains the experimental results.