Exploring point defects in hexagonal boron‐nitrogen monolayers

Abstract

A comprehensive theoretical study of selected point defects for a monolayer of hexagonal boron nitride (h‐BN) is presented. Two‐dimensional structures were simulated through large h‐BN molecular clusters and used to examine various defects, like: atom vacancies, atom substitutions, or distortions of the hexagonal lattice. Since carbon contaminations are very common in the h‐BN technology, a particular attention has been paid to carbon impurities. The calculations of IR spectra for the doped molecular clusters reveal the presence of additional frequencies, which in many cases correspond to defect‐bound modes. In particular, when two carbon atoms are close to each other, a localized stretching CC mode of a high intensity has been found, with a frequency value of about 100‐200 cm–1 higher than for collective BN stretch frequencies. Absorption UV‐Vis spectra obtained from time‐dependent density functional theory show that the inclusion of impurities results in an emergence of several low‐energy electronic excitations, from which some are localized on a defect, while other are delocalized. Energies of these excitations are strongly dependent on the defect type, and they range from about 0.7 to 6.1 eV for the lowest excitations. Based on UV‐Vis spectra we propose several candidates which could be responsible for the experimental 4 eV color band. These defects are built from two or four adjacent carbon atoms and have the lowest excitation ranging from 3.9 to 4.8 eV, which is strongly localized on the defect.

From 2-D to 0-D Boron Nitride Materials, The Next Challenge

“…an anti-site nitrogen-vacancy (nitrogen occupies a boron site, and there is a vacancy at the nitrogen site) [36]. In the framework of quantum computing, group analysis along with DFT calculations demonstrated that the neutral paramagnetic carbon defect C B V N could be a valid candidate for spin coherent manipulation and qubit, as well as C N V B [39,40,41]. Recently, Weston et al attributed the single-photon emission in the UV and at about 2 eV to carbon substituting nitrogen and interstitial centers, respectively [42].…”

Luminescence properties of hexagonal boron nitride powders probed by deep UV photoluminescence spectroscopy

“…[ 23 ] showed that the 4.1 eV luminescence peak could be caused by the carbon dimer defect (C B C N ), which is a complex formed by two impurity carbon atoms on nearest-neighbor sites in the h-BN lattice. Another theoretical study using quantum chemistry calculations on h-BN monolayer suggested that carbon clusters from two to four atoms such as C B C N , C 4 cis , and C 4 trans defects give luminescence in the range of 3.9 to 4.8 eV [ 24 ]. Thus, the sharp emission lines observed in the UV region could be related to carbon defects which are generated during the annealing process.…”

Boron nitride for excitonics, nano photonics, and quantum technologies

“…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.…”