  Spin-active defects in silicon carbide (SiC) are promising quantum light
sources for realizing scalable quantum technologies. In different applications,
these photoluminescent defects are often placed in a nanostructured host or
close to surfaces in order to enhance the signal from the defects. However,
proximity to the surface not only modifies frequencies of the quantum emission
from the defect, but also adversely affects their photo-stability, resulting in
blinking and/or photobleaching of the defect. These effects can be ameliorated
by passivating surfaces with optimal adsorbates. In this work, we explore
different passivation schemes using density functional theory-based
calculations. We show that a uniform surface passivation with either hydrogen
or with mixed hydrogen/hydroxyl groups completely removes surface states from
the SiC band gap, restoring the optical properties of the defects.
