First-Principles Investigation of Surface-Induced Effects on the Properties of Divacancy Qubits in 3C-SiC
Neutral silicon-carbon divacancy (V$_{Si}$V$_{C}$) in cubic silicon carbide (3C-SiC) is a promising class of point defects for quantum technologies based on active crystalline centers. Within the theoretical framework of spin-polarized Density Functional Theory (DFT), this study examines the structural and electronic characteristics of V$_{Si}$V$_{C}$ centers near a hydrogen-terminated Si-rich (001) surface. A (2x1):H reconstructed slab of 628 atoms represents the near-surface environment, with divacancies located at depths ranging from 0.6 to 1.2 nm in basal and axial orientations. The optimized geometries show localized relaxations, and the electronic structure reveals in-gap defect levels in both spin channels. Furthermore, examination of the zero-field splitting (ZFS) tensor demonstrates sensitivity to the orientation of the spin defects and their distance from the surface. The findings of this investigation suggest that surface proximity exerts a substantial influence on the spin Hamiltonian of divacancies, providing insight for the engineering of SiC-based qubits and nanoscale quantum devices.