Dimensionality-Driven Charge Stabilization of Group-IV Color Centers in Diamond Ultrathin Films

Neutral group-IV vacancy (XV, X = Si, Ge, Sn, and Pb) centers in diamond are promising solid-state spin-photon interfaces owing to favorable spin coherence and inversion-symmetry-protected optical transitions. However, stabilizing their neutral charge state typically requires stringent Fermi-level engineering in high-purity boron-doped diamond, which poses significant materials-growth challenges. Here, dimensional confinement in diamane offers an alternative for charge-state stabilization without intentional doping. Our results show that diamane thickness and surface chemical termination cooperatively tune the electronic structures of XV centers, while their neutral-state thermodynamic stability is enhanced. The zero-field splitting and spin–orbit coupling of XV centers could be tuned while largely preserving their optical transition energies. We find hydrogenated diamane offers the best balance between charge-state stability and magneto-optical performance. More broadly, our findings establish dimensional confinement as a general strategy for engineering the charge, optical, and spin properties of solid-state quantum defects.