  Color centers in silicon carbide (SiC) have demonstrated significant promise
for quantum information processing. However, the undesirable ionization process
that occurs during optical manipulation frequently causes fluctuations in the
charge state and performance of these defects, thereby restricting the
effectiveness of spin-photon interfaces. Recent predictions indicate that
divacancy defects near stacking faults possess the capability to stabilize
their neutral charge states, thereby providing robustness against
photoionization effects. In this work, we present a comprehensive protocol for
the scalable and targeted fabrication of single divacancy arrays in 4H-SiC
using a high-resolution focused helium ion beam. Through photoluminescence
emission (PLE) experiments, we demonstrate long-term emission stability with
minimal linewidth shift ($\sim$ 50 MHz over 3 hours) for the single c-axis
divacancies within stacking faults. By measuring the ionization rate for
different polytypes of divacancies, we found that the divacancies within
stacking faults are more robust against resonant excitation. Additionally,
angle-resolved PLE spectra reveal their two resonant-transition lines with
mutually orthogonal polarizations. Notably, the PLE linewidths are
approximately 7 times narrower and the spin-coherent times are 6 times longer
compared to divacancies generated via carbon-ion implantation. These findings
highlight the immense potential of SiC divacancies for on-chip quantum
photonics and the construction of efficient spin-to-photon interfaces,
indicating a significant step forward in the development of quantum
technologies.
