Theoretical studies on the stabilization and diffusion behaviors of helium impurities in 6H-SiC by DFT calculations

In fusion environments, large scales of helium (He) atoms are produced by a radical transformation along with structural damage in structural materials, resulting in material swelling and degradation of physical properties. To understand its irradiation effects, this paper investigates the stability, electronic structure, energetics, charge density distribution, PDOS and TDOS, and diffusion processes of He impurities in 6H-SiC materials. The formation energy indicates that a stable, favorable position for interstitial He is the HR site with the lowest energy of 2.40 eV. In terms of vacancy, the He atom initially prefers to substitute at pre-existing Si vacancy than C vacancy due to lower substitution energy. The minimum energy paths (MEPs) with migration energy barriers are also calculated for He impurity by interstitial and vacancy-mediated diffusion. Based on its calculated energy barriers, the most possible diffusion path includes the exchange of interstitial and vacancy sites with effective migration energies ranging from 0.101 eV to 1.0 eV. Our calculation provides a better understanding of the stabilization and diffusion behaviors of He impurities in 6H-SiC materials.& COPY; 2023 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This paper investigates the stability, electronic structure, energetics, charge density distribution, PDOS and TDOS, and diffusion processes of He impurities in 6H-SiC materials. The results show that the most stable position for interstitial He is the HR site with a formation energy of 2.40 eV, and He atom prefers to substitute at pre-existing Si vacancy rather than C vacancy. The calculated energy barriers suggest that the most possible diffusion path involves the exchange of interstitial and vacancy sites with migration energies ranging from 0.101 eV to 1.0 eV. This study provides a better understanding of the stabilization and diffusion behaviors of He impurities in 6H-SiC materials.