Carbon dimer defect as a source of the 4.1 eV luminescence in hexagonal boron nitride

Abstract

We propose that the carbon dimer defect CBCN in hexagonal boron nitride gives rise to the ubiquitous narrow luminescence band with a zero-phonon line of 4.08 eV (usually labeled the 4.1 eV band). Our first-principles calculations are based on hybrid density functionals that provide a reliable description of wide band-gap materials. The calculated zero-phonon line energy of 3.8 eV is close to the experimental value, and the deduced Huang-Rhys factor of S ≈ 2.0, indicating modest electron-phonon coupling, falls within the experimental range. The optical transition occurs between two localized π-type defects states, with a very short radiative lifetime of 1.7 nanoseconds, in very good accord with experiments.

Giant shift upon strain on the fluorescence spectrum of VNNB color centers in h-BN

“…The wide band gap of h-BN makes it an insulator that can host highquality emitters and allows for combination with other materials as substrates 13 . The experiments for exploring the nature of the emission of these color centers started with their first observations 10,[14][15][16][17][18][19][20][21][22][23][24][25] and recent theoretical works have provided evidence that the SPEs are indeed color centers, i.e., local point defects [26][27][28][29][30] .…”

Boron nitride for excitonics, nano photonics, and quantum technologies

“…Of course such dipole is weak or it vanishes. But we believe that measuring the emission diagrams of such defects, which Chris van de Walle and his colleague explicitly ask for, will boost the understanding to unexplored degrees [142]. Of course it is difficult but science is not exciting if not challenging.…”

“…Nothing specific is observed except the rise of a series of peaks at 4.1 eV when growth conditions depart from using ultra pure B and N precursor. These peaks were initially attributed to carbon incorporation in the lattice [135] but this interpretation is no longer shared [136][137][138][139][140][141][142][143]. It is obvious that it is related to a probable influence of the impurities of the precursors that impact the formation of a perfect crystal or contaminate it.…”

Stone–Wales defects in hexagonal boron nitride as ultraviolet emitters

“…This can affect the optimized geometry in the excited state and the total energy of the 1 A 0 (e) state. The latter can be corrected by estimating the exchange energy by the calculated DFT total energies of the singlet and triplet excited states similarly to a previous work 16 . At the ground state geometry, the corrected excitation energy is 4.53 eV, which is reduced by 0.47 eV in the geometry optimization procedure.…”

“…We note that the radiative lifetime of another UV emitter in h-BN, the carbon-dimer defect (see below), was derived similarly in ref. 16 . We conclude from the calculated ZPL energy, characteristic phonon replica in the phonon sideband, and the optical lifetime that the 4.08-eV quantum emitter can be associated with the pentagon-heptagon Stone-Wales defect in h-BN.…”