Bistable carbon-vacancy defects in $h$-BN

Abstract

Single photon emitters in hexagonal boron nitride have been extensively studied recently. Although unambiguous identification of the emitters is still under intense research, carbon related defects are believed to play a vital role for the emitter producing zero-phonon-lines in the range of $1.6$ to $2.2$~eV. In this study, we systematically investigate two configurations of carbon-vacancy defects, VNCB and CNVB, by means of density functional theory calculations. We calculated the reaction barrier energies from one defect to the other to determine relative stability. We find the barrier energies are charge dependent and CNVB could easily transform to VNCB in neutral and positive charge states while it is stable when negatively charged. Formation energy calculations show that the VNCB is the dominant defect over CNVB. However, neither VNCB nor CNVB has suitable fluorescence spectra that could reproduce the observed ones. Our results indicate that the origin of the $1.6$-to-$2.2$-eV emitters should be other carbon-related configurations.

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• First-principles theory of the luminescence lineshape for the triplet transition in diamond NV centre
• Defect-related photoluminescence of hexagonal boron nitride
• Towards $\text{ab initio}$ identification of paramagnetic substitutional carbon defects in hexagonal boron nitride acting as quantum bits
• Origin of nonclassical light emission from defects in multi-layer hexagonal boron nitride