Non-radiative energy transfer between boron vacancies in hexagonal boron nitride and other 2D materials

TL;DR

This study probes non-radiative energy transfer from VB− centers in ultrathin hBN to 2D absorbers like graphene and TMDs. Using a Green's-function electrodynamical model for a 0D emitter near a stratified hBN/graphene/SiO2/Si stack, the authors quantify how FRET competes with intrinsic non-radiative decay. They find that FRET is negligible for hBN thicknesses above ~3 nm and completely suppressed when adjacent 2D semiconductors have band gaps above the VB− emission energy (~1.5 eV), revealing that VB− centers are suitable for ultra-thin quantum sensing in vdW heterostructures. By fitting TRPL and quenching data, they extract Γ_0^hBN ≈ (1.35 ± 0.68)×10^5 s⁻¹, confirming the observed weak PL arises from intrinsically low quantum yield, not from enhanced non-radiative decay at interfaces.

Abstract

Boron vacancies ($V_B^-$) in hexagonal boron nitride (hBN) have emerged as a promising platform for two-dimensional quantum sensors capable of operating at atomic-scale proximity. However, the mechanisms responsible for photoluminescence quenching in thin hBN sensing layers when placed in contact with absorptive materials remain largely unexplored. In this Letter, we investigate non-radiative Förster resonance energy transfer (FRET) between $V_B^-$ centers and either monolayer graphene or 2D semiconductors. Strikingly, we find that the FRET rate is negligible for hBN sensing layers thicker than 3 nm, highlighting the potential of $V_B^-$ centers for integration into ultra-thin quantum sensors within van der Waals heterostructures. Furthermore, we experimentally extract the intrinsic radiative decay rate of $V_B^-$ defects.

Figures (9)

• Figure 1: a) Sketch of the decay rates of a $V_{B}^{-}$ center close to graphene. ES and GS are the excited and ground states of the defect, $\Gamma_{0}$ is the radiative decay rate, $\Gamma_{\mathrm{nr}}$ is the relaxation rate to the metastable state m and $\Gamma_{\mathrm{FRET}}$ the FRET rate between the emitter and graphene. b) Sketch of the samples.
• Figure 2: a,d) Optical image of a 5 and 2 nm hBN flake partially deposited on MLG and SiO$_2$/Si. b,e) Corresponding cw PL raster scans. c,f) TRPL data and fits.
• Figure 3: a) Sketch of the structure used for calculating the decay rate. b) Quenching factor defined by Eq. \ref{['Quenchdef']} (data are shown in red points, results of the model for three values of $\Gamma^{\mathrm{hBN}}_{0}$ are shown by the green, purple and orange lines. c) $\Gamma^{\mathrm{hBN}}_{0}$ extracted from the TRPL data for each sample.
• Figure 4: a) Sketch of the sample to study FRET between $V_{B}^{-}$ centers and TMDs. b) TRPL data of a 2 nm hBN flake on top of SiO$_2$/Si, MoS$_2$ and MoTe$_2$. $\mathrm{E_g^{MoS_2}}$, $\mathrm{E_g^{MoS_2}}$ and $\mathrm{E_g^{V_B^-}}$ are the band gap energies of MoS$_2$, MoTe$_2$ and the emission energy of the $V_{B}^{-}$ centers.
• Figure S1: Optical images and cw-PL raster scans for all samples. The scale bars is 5 $\textmu$m.