Combining experiments on luminescent centres in hexagonal boron nitride with the polaron model and ab initio methods towards the identification of their microscopic origin

Abstract

The two-dimensional material hexagonal boron nitride (hBN) hosts luminescent centres with emission energies of ∼ 2 eV which exhibit pronounced phonon sidebands. We investigate the microscopic origin of these luminescent...

Color Centers in Hexagonal Boron Nitride Nanosheet-Based Heterojunctions: Implications for Quantum Emitters and Ultrathin Sensors

“…At present, apart from the V B –1 ensemble in the hBN flake, the atomic structures of the other luminescence defects or quantum emitters in hBN are speculative based on the DFT calculations and PL spectra. For example, it is not found that V N 21 and the majority of carbon-related color centers − in hBN have ODMR signals; thus, these defects can only be identified by the PL spectra coupled with DFT calculations.…”

“…At first, the negatively charged complex defect of a V B and a substitutional carbon of the nitrogen site (V B C N –1 ) was considered as a possible candidate . Until very recently, a few theoretical investigations show that maybe the carbon-related color centers with a ZPL at around ∼580 nm are related to a carbon trimer defect with three substitutional carbon atoms (C B C N2 ) − , and a carbon tetramer defect with three substitutional carbon atoms (C N C B3 ). , Therefore, the atomic-scale structures of the carbon-related defects are still speculative and controversial, ,− ,,, and more advanced experiments and theoretical calculations should be carried out. As shown in Figure and Table , here we calculated the single-particle electronic structures, ZPL, and absorption energies of C B C N2 and C N C B3 .…”

“…Color centers in hexagonal boron nitride (hBN) have been applied for a single-photon source and quantum sensing, as well as nuclear spin polarization and control, due to their ultrahigh brightness or spin-dependent magnetic-optical properties at room temperature. − In particular, the negatively charged boron vacancy (V B –1 ) color centers in hBN are attracting more and more attention, due to their diverse fabrication methods and the promising sensing applications of the V B –1 ensemble. − However, due to the low quantum efficiency, it is almost impossible to use a V B –1 defect as a single-photon emitter, although various plasmonic microcavities can effectively tune and enhance the photoluminescence (PL) intensity of the V B –1 defect. − Nevertheless, various luminescence defects have been explored in recent years for single-photon emitters or sensors, which are related to vacancy, antisite, carbon-related, or oxygen-related defects, or their complexes of those point defects in hBN, and which cover ultraviolet-to-visible spectral regions. − …”

“…Carbon-related defects in hBN have been proven to be ultrabright single-photon emitters − and potential spin defects for nanoscale quantum sensing. − Ion implantation and subsequent annealing, high-temperature annealing of hBN nanoflakes, , electron-beam irradiation, , and the introduction of carbon doping during material synthesis have been used to activate carbon-related quantum emitters. However, carbon-related defects are randomly distributed in different hBN flakes after high-temperature annealing; therefore, it is difficult to fabricate identical emitters at designated sites in nanometer-thick and even monolayer hBN, which hinders the integration of these defects in two-dimensional quantum-optical devices. − Moreover, the atomic structures of carbon-related defects in hBN are speculative or unknown, although many defects, such as carbon dimer, trimer, and tetramer, are considered to be promising candidates by combining group theory with density functional theory (DFT) calculations. − …”

High-Throughput Search for Triplet Point Defects with Narrow Emission Lines in 2D Materials

“…Hence, the predicted ZPL energies should be considered as a lower bound. However, even if the ZPL is underestimated, the calculated line shape of the PL spectra, which is governed by the electron–phonon coupling, is more reliable and can be used to identify specific defects centers. , It is also well-known that DFT sometimes struggles to predict the correct ground state spins of defects and/or molecular complexes involving transition metal atoms. This is especially true for metal atoms belonging to period three of the periodic table with partially filled 3d states.…”