Photoluminescence, photophysics, and photochemistry of the VB− defect in hexagonal boron nitride

Abstract

Extensive photochemical and spectroscopic properties of the V − B defect in hexagonal boron nitride are calculated, concluding that the observed photoemission associated with recently observed optically detected magnetic resonance is most likely of (1) 3 E → (1) 3 A 2 origin. Rapid intersystem crossing from the defect's triplet to singlet manifolds explains the observed short excited-state lifetime and very low quantum yield. New experimental results reveal smaller intrinsic spectral bandwidths than previously recognized, interpreted in terms of spectral narrowing and zero-phonon-line shifting induced by the Jahn-Teller effect. Different types of computational methods are applied to map out the complex triplet and singlet defect manifolds, including the doubly ionized formulation of the equation-of-motion coupled-cluster theory that is designed to deal with the open-shell nature of defect states, and mixed quantum-mechanics/molecular-mechanics schemes enabling 5763-atom simulations. Two other energetically feasible spectral assignments from among the singlet and triplet manifolds are considered, but ruled out based on inappropriate photochemical properties.

Cavity quantum electrodynamics design with single photon emitters in hexagonal boron nitride

“…Here, we consider two types of defect sites, negatively charged boron vacancy (V B − ) and carbon-related center (V N C B ), which have been proposed to interpret the recent observation of optically detected magnetic resonance (ODMR). 15,16,31,32 As predicted in Ref. 31, V B − center could give rise to six intrinsic orbital levels and the triplet transition (1) 3 E′ → (1) 3 A 2 ′ with dominant (1) 3 A 2 → (1) 3 A 2 ′ component, of which transition energy ΔE=1.78-1.83 eV agrees well with the emission detected around 680 nm (Fig.…”

“…An in-depth understanding of SPEs could be gained by comparing them with ab initio calculations. 30,31,32 Distinct from the well-studied defect-related SPEs in three-dimensional (3D) WBG crystals, such as nitrogen vacancy (NV) centers in diamond, 3 silicon vacancy (V Si ) and divacancy (DV) centers in silicon carbide, 4,5 the atomic origin of emission in h-BN is still under debate. Here, we consider two types of defect sites, negatively charged boron vacancy (V B − ) and carbon-related center (V N C B ), which have been proposed to interpret the recent observation of optically detected magnetic resonance (ODMR).…”

Density functionals with asymptotic-potential corrections are required for the simulation of spectroscopic properties of materials

“…Calculations on model compounds for defects in 2D materials show very rapid convergence of calculated electronic properties with respect to increasing sample size for transitions localised within the defect. 65,66,72 Of significance, model-compound calculations have also been shown to converge to the same results as obtained using analogous calculations on 2D periodic defect models. 72,75 Nevertheless, these generic results are not expected to apply to the charge-transfer transitions of V -N considered herein.…”

“…[49][50][51][52] Indeed, defects in h-BN have been associated with single-photon emission (SPE) [53][54][55][56] and optically detected magnetic resonance (ODMR). 57,58 Historically, only defects displaying magnetic properties have had their chemical natures determined, 57,[59][60][61][62][63][64][65] but recently came the first characterization based only on observed spectral properties. 66 This was made possible through extensive experimental characterization of composition, combined with computational spectroscopic predictions.…”

Accurate prediction of the properties of materials using the CAM‐B3LYP density functional

“…[33][34][35][36] Whereas research on defects in diamond and silicon carbide has historically been prominent, 35,37 of immediate concern are defects in hexagonal boron nitride (h-BN), which can display single-photon emission [38][39][40][41] and optically detected magnetic resonance (ODMR). 42,43 Calculations have been essential in the determination of the chemical nature of defects and their intricate magnetic, photophysical, and photochemical properties, [44][45][46][47][48] with ones successful in spectroscopic modeling using advanced methods such as CAM-B3LYP and or ab initio coupled-cluster approaches 45,46,48 or else mixed DFT and ab initio methods. 47 Even though calculations on localized-defect transitions using molecular models converge very quickly with increasing sample size 49 to the (more slowly converging) results from 2D simulations, charge-transfer properties can be of interest that can only be modeled using periodic models.…”