First-Principles Investigation of Near-Surface Divacancies in Silicon Carbide

The realization of quantum sensors using spin defects in semiconductors requires a thorough understanding of the physical properties of the defects in the proximity of surfaces. We report a study of the divacancy (VSiVC) in 3C-SiC, a promising material for quantum applications, as a function of surface reconstruction and termination with -H, -OH, -F and oxygen groups. We show that a VSiVC close to hydrogen-terminated (2 x 1) surfaces is a robust spin-defect with a triplet ground state and no surface states in the band gap and with small variations of many of its physical properties relative to the bulk, including the zero-phonon line and zero-field splitting. However, the Debye-Waller factor decreases in the vicinity of the surface and our calculations indicate it may be improved by strain-engineering. Overall our results show that the VSiVC close to SiC surfaces is a promising spin defect for quantum applications, similar to its bulk counterpart.