Quantum Light in Curved Low Dimensional Hexagonal Boron Nitride Systems

Abstract

Low-dimensional wide bandgap semiconductors open a new playing field in quantum optics using sub-bandgap excitation. In this field, hexagonal boron nitride (h-BN) has been reported to host single quantum emitters (QEs), linking QE density to perimeters. Furthermore, curvature/perimeters in transition metal dichalcogenides (TMDCs) have demonstrated a key role in QE formation. We investigate a curvature-abundant BN system – quasi one-dimensional BN nanotubes (BNNTs) fabricated via a catalyst-free method. We find that non-treated BNNT is an abundant source of stable QEs and analyze their emission features down to single nanotubes, comparing dispersed/suspended material. Combining high spatial resolution of a scanning electron microscope, we categorize and pin-point emission origin to a scale of less than 20 nm, giving us a one-to-one validation of emission source with dimensions smaller than the laser excitation wavelength, elucidating nano-antenna effects. Two emission origins emerge: hybrid/entwined BNNT. By artificially curving h-BN flakes, similar QE spectral features are observed. The impact on emission of solvents used in commercial products and curved regions is also demonstrated. The ‘out of the box’ availability of QEs in BNNT, lacking processing contamination, is a milestone for unraveling their atomic features. These findings open possibilities for precision engineering of QEs, puts h-BN under a similar ‘umbrella’ of TMDC’s QEs and provides a model explaining QEs spatial localization/formation using electron/ion irradiation and chemical etching.

Stable emission and fast optical modulation of quantum emitters in boron nitride nanotubes

“…Most of them bleach within 10 seconds. This is consistent with former results [13] and is likely due to a much larger curvature in 5-nm-diameter BNNTs.…”

“…Moreover, a recent work reported single photon emission from bundles of boron nitride nanotubes (BNNTs) with an average diameter of 5 nm [13]. It reports bleaching under 532 nm excitation, and notes the bleaching can be alleviated with N,N'-Dimethylacetamide (DMAc) solutions and indium tin oxide (ITO) substrates [13].…”

Atomically Thin Hexagonal Boron Nitride and Its Heterostructures

“…[ 141,142 ] The dilemma has long plagued researchers, [ 13,136–138 ] while it was identified by the two‐photon excitation spectroscopy recently. [ 143 ] According to the spectra, the bright deep‐UV emission has been attributed to the strong coupling of exciton–phonon interactions in h‐BN. [ 144 ] This efficient exciton–phonon interactions will generate sub‐nanosecond timescale of recombination, in turn, and enable an intense of deep‐UV emission.…”

Confinement of Dyes inside Boron Nitride Nanotubes: Photostable and Shifted Fluorescence down to the Near Infrared

“…The synthesis begins by cutting raw BNNTs (BNNT LLC supplier) using mechanical grinding and ultrasound treatments. The resulting material is then purified in nitric acid and annealed at high temperature in air [ 28 ] to suppress photoluminescence background from BN defects and B x O y impurities [ 29 ] (Figure S1, Supporting information). The last step is a liquid phase encapsulation of a selected dye molecule, for example, DPP2 (Figure 1a), in thus processed BNNTs, followed by a thorough rinsing in dimethylformamide (DMF)/toluene and finally briefly in a piranha solution at room temperature to remove excess of dye molecules.…”