Photoluminescent properties of the carbon-dimer defect in hexagonal boron-nitride: A many-body finite-size cluster approach Article Swipe
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· 2021
· Open Access
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· DOI: https://doi.org/10.1103/physrevmaterials.5.095201
· OA: W3184464971
We study the carbon dimer defect in a hexagonal boron-nitride monolayer using\nthe GW and Bethe-Salpeter many-body perturbation theories within a finite size\ncluster approach. While quasiparticle energies converge very slowly with system\nsize due to missing long-range polarization effects, optical excitations\nconverge much faster, with a $1/R^3$ scaling law with respect to cluster\naverage radius. We obtain a luminescence zero-phonon energy of 4.36 eV,\nincluding significant 0.13 eV zero-point vibrational energy and 0.15 eV\nreorganization energy contributions. Inter-layer screening decreases further\nthe emission energy by about 0.3 eV. These results bring support to the recent\nidentification of the substitutional carbon dimer as the likely source of the\nzero-phonon 4.1 eV luminescence line. Finally, the GW quasiparticle energies\nare extrapolated to the infinite h-BN monolayer limit, leading to a predicted\ndefect HOMO-LUMO photoemission gap of 7.6 eV. Comparison with the optical gap\nyields a very large excitonic binding energy of 3 eV for the associated\nlocalized Frenkel exciton.\n
