Duong, NMH, Glushkov, E, Chernev, A, Navikas, V, Comtet, J, Nguyen, MAP, Toth, M, Radenovic, A, Tran, TT & Aharonovich, I 2019, 'Facile Production of Hexagonal Boron Nitride Nanoparticles by Cryogenic Exfoliation.', Nano letters, vol. 19, no. 8, pp. 5417-5422.View/Download from: Publisher's site
Fluorescent nanoparticles with optically robust luminescence are imperative to applications in imaging and labeling. Here we demonstrate that hexagonal boron nitride (hBN) nanoparticles can be reliably produced using a scalable cryogenic exfoliation technique with sizes below 10 nm. The particles exhibit bright fluorescence generated by color centers that act as atomic-size quantum emitters. We analyze their optical properties, including emission wavelength, photon-statistics, and photodynamics, and show that they are suitable for far-field super-resolution fluorescence nanoscopy. Our results provide a foundation for exploration of hBN nanoparticles as candidates for bioimaging, labeling, as well as biomarkers that are suitable for quantum sensing.
Duong, NMH, Regan, B, Toth, M, Aharonovich, I & Dawes, J 2019, 'A Random Laser Based on Hybrid Fluorescent Dye and Diamond Nanoneedles', physica status solidi (RRL) - Rapid Research Letters, vol. 13, no. 2.View/Download from: Publisher's site
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Random lasers use radiative gain and multiple scatterers in disordered media to generate light amplification. In this study, a random laser based on diamond nanoneedles that act as scatterers in combination with fluorescent dye molecules that serve as a gain medium has been demonstrated. Random lasers realized using diamond possess high spectral radiance with angle-free emission and thresholds of 0.16 mJ. The emission dependence on the pillar diameter and density is investigated, and optimum lasing conditions are measured for pillars with spacing and density of ≈336 ± 40 nm and ≈2.9 × 1010 cm−2. Our results expand the application space of diamond as a material platform for practical, compact photonic devices, and sensing applications.
Kim, S, Duong, NMH, Nguyen, M, Lu, TJ, Kianinia, M, Mendelson, N, Solntsev, A, Bradac, C, Englund, DR & Aharonovich, I 2019, 'Integrated on Chip Platform with Quantum Emitters in Layered Materials', Advanced Optical Materials, vol. 7, no. 23.View/Download from: Publisher's site
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Integrated quantum photonic circuitry is an emerging topic that requires efficient coupling of quantum light sources to waveguides and optical resonators. So far, great effort is devoted to engineering on-chip systems from 3D crystals such as diamond or gallium arsenide. In this study, room-temperature coupling is demonstrated of quantum emitters embedded in layered hexagonal boron nitride to an on-chip aluminum nitride waveguide. 1.35% light coupling efficiency is achieved in the device and transmission of single photons through the waveguide is demonstrated. The results serve as foundation for integrating layered materials to on-chip components and realizing integrated quantum photonic circuitry.
Ngoc My Duong, H, Nguyen, MAP, Kianinia, M, Ohshima, T, Abe, H, Watanabe, K, Taniguchi, T, Edgar, JH, Aharonovich, I & Toth, M 2018, 'Effects of High-Energy Electron Irradiation on Quantum Emitters in Hexagonal Boron Nitride.', ACS Applied Materials and Interfaces, vol. 10, no. 29, pp. 24886-24891.View/Download from: Publisher's site
Hexagonal boron nitride (hBN) mono and multilayers are promising hosts for room-temperature single photon emitters (SPEs). In this work we explore high-energy (∼MeV) electron irradiation as a means to generate stable SPEs in hBN. We investigate four types of exfoliated hBN flakes-namely, high-purity multilayers, isotopically pure hBN, carbon-rich hBN multilayers and monolayered material-and find that electron irradiation increases emitter concentrations dramatically in all samples. Furthermore, the engineered emitters are located throughout hBN flakes (not only at flake edges or grain boundaries) and do not require activation by high-temperature annealing of the host material after electron exposure. Our results provide important insights into controlled formation of hBN SPEs and may aid in identification of their crystallographic origin.
Duong, NMH, Xu, Z-Q, Kianinia, M, Su, R, Liu, Z, Kim, S, Bradac, C, Li, L-J, Solntsev, A, Liu, J & Aharonovich, I 2018, 'Enhanced Emission from WSe2 Monolayers Coupled to Circular Bragg Gratings', ACS Photonics, vol. 5, pp. 3950-3955.View/Download from: Publisher's site
Two-dimensional transition-metal dichalcogenides (TMDC) are of great interest
for on-chip nanophotonics due to their unique optoelectronic properties. Here,
we propose and realize coupling of tungsten diselenide (WSe2) monolayers to
circular Bragg grating structures to achieve enhanced emission. The interaction
between WSe2 and the resonant mode of the structure results in Purcell-enhanced
emission, while the symmetric geometrical structure improves the directionality
of the out-coupling stream of emitted photons. Furthermore, this hybrid
structure produces a record high contrast of the spin valley readout (> 40%)
revealed by the polarization resolved photoluminescence (PL) measurements. Our
results are promising for on-chip integration of TMDC monolayers with optical
resonators for nanophotonic circuits.
Bishop, J, Fronzi, M, Elbadawi, C, Nikam, V, Pritchard, J, Fröch, JE, Duong, NMH, Ford, MJ, Aharonovich, I, Lobo, CJ & Toth, M 2018, 'Deterministic Nanopatterning of Diamond Using Electron Beams.', ACS nano, vol. 12, no. 3, pp. 2873-2882.View/Download from: Publisher's site
Diamond is an ideal material for a broad range of current and emerging applications in tribology, quantum photonics, high-power electronics, and sensing. However, top-down processing is very challenging due to its extreme chemical and physical properties. Gas-mediated electron beam-induced etching (EBIE) has recently emerged as a minimally invasive, facile means to dry etch and pattern diamond at the nanoscale using oxidizing precursor gases such as O2 and H2O. Here we explain the roles of oxygen and hydrogen in the etch process and show that oxygen gives rise to rapid, isotropic etching, while the addition of hydrogen gives rise to anisotropic etching and the formation of topographic surface patterns. We identify the etch reaction pathways and show that the anisotropy is caused by preferential passivation of specific crystal planes. The anisotropy can be controlled by the partial pressure of hydrogen and by using a remote RF plasma source to radicalize the precursor gas. It can be used to manipulate the geometries of topographic surface patterns as well as nano- and microstructures fabricated by EBIE. Our findings constitute a comprehensive explanation of the anisotropic etch process and advance present understanding of electron-surface interactions.