Interaction between helium and intrinsic point defects in 3C-SiC single crystal

Abstract

Silicon carbide (SiC) is a candidate structural material for fission and fusion reactors as well as an important wide band-gap semiconductor for electronic devices. Using first-principles calculations, we systemically investigate the energetics and stability of helium (He) atoms and intrinsic point defects inside single-crystalline 3C-SiC. We find that the formation energy of interstitial He is lower than those of point defects. Inside 3C-SiC, the He-C interaction is stronger than He-Si. Hence, the interstitial He atom in the Si tetrahedral site has a stronger interaction with the six C atoms in the second nearest neighbor than the four nearest neighboring Si atoms. For interstitial He atoms, the equilibrium He-He distance is about 1.81 Å with a weak attraction of 0.09 eV. According to the binding energies of Hen (n = 2–4) clusters, He interstitials can form He bubbles without involving other types of structural defects. Moreover, a Si (C) monovacancy can accommodate up to 11 (9) He atoms. The Hen clusters trapped in the Si or C monovacancy induce large internal pressure in the order of magnitude of GPa and thus facilitate the creation of a new vacancy at the nearby lattice site.