First-principles investigation of near surface divacancies in 3C-SiC

The realization of quantum sensors using spin defects in semiconductors requires a thorough understanding of the physical properties of the defects in proximity of surfaces. Here we focus on silicon carbide (SiC), a promising material for quantum applications. We report a first-principles study of the divacancy (V_SiV_C) in 3C-SiC as a function of surface reconstruction and termination with -H, -OH, -F and oxygen groups. We show that a divacancy close to hydrogen-terminated (2×1) surfaces is a robust spin-defect with a triplet ground state, 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 divacancy close to SiC surfaces is a promising spin defect for quantum applications, similar to its bulk counterpart.