Ab initio and group theoretical study of properties of a carbon trimer defect in hexagonal boron nitride

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

“…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. − …”

Rare isotope-containing diamond colour centres for fundamental symmetry tests

“…Because both defects have normalC2v symmetry, the states that the single electron orbitals can take on can transform like false(A1,A2,B1,B2false). These are all orbital singlets, and thus the orbital angular momentum, L, is zero for these states [67,68]. As a result, the spin–orbit coupling which is proportional to L⋅S is zero.…”

Spin-active defects in hexagonal boron nitride

“…Carbon trimers. Carbon trimers including C 2 C N and C 2 C B were found energetically favorable and proposed to explain some experimental results [165,166,170,171]. Both C 2 C N and C 2 C B have doublet GS (S = 1/2) [166], in particular Golami et al [171] proposed that C 2 C N has quartet substate (S = 3/2).…”