KeywordsHexagonal boron nitride, multilayer, single photon source, multicolor, room temperature. AbstractHexagonal boron nitride (hBN) is an emerging two dimensional material for quantum photonics owing to its large bandgap and hyperbolic properties. Here we report a broad range of multicolor room temperature single photon emissions across the visible and the near infrared spectral ranges from point defects in hBN multilayers. We show that the emitters can be categorized into two general groups, but most likely possess similar crystallographic structure. We further show two approaches for engineering of the emitters using either electron beam irradiation or annealing, and characterize their photophysical properties. The emitters exhibit narrow line widths of sub 10 nm at room temperature, and a short excited state lifetime with high brightness. Remarkably, the emitters are extremely robust and withstand aggressive annealing treatments in oxidizing and reducing environments. Our results constitute the first step towards deterministic engineering of single emitters in 2D materials and hold great promise for the use of defects in boron nitride as sources for quantum information processing and nanophotonics.

Development of scalable quantum photonic technologies requires on-chip integration of photonic components. Recently, hexagonal boron nitride (hBN) has emerged as a promising platform, following reports of hyperbolic phonon-polaritons and optically stable, ultra-bright quantum emitters. However, exploitation of hBN in scalable, on-chip nanophotonic circuits and cavity quantum electrodynamics (QED) experiments requires robust techniques for the fabrication of high-quality optical resonators. In this letter, we design and engineer suspended photonic crystal cavities from hBN and demonstrate quality (Q) factors in excess of 2000. Subsequently, we show deterministic, iterative tuning of individual cavities by direct-write EBIE without significant degradation of the Q-factor. The demonstration of tunable cavities made from hBN is an unprecedented advance in nanophotonics based on van der Waals materials. Our results and hBN processing methods open up promising avenues for solid-state systems with applications in integrated quantum photonics, polaritonics and cavity QED experiments.

Color centers in hexagonal boron nitride (hBN) are becoming an increasingly important building block for quantum photonic applications. Herein, we demonstrate the efficient coupling of recently discovered spin defects in hBN to purposely designed bullseye cavities. We show that the allmonolithic hBN cavity system exhibits an order of magnitude enhancement in the emission of the coupled boron vacancy spin defects. In addition, by comparative finite-difference time-domain modelling, we shed light on the emission dipole orientation, which has not been experimentally demonstrated at this point. Beyond that, the coupled spin system exhibits an enhanced contrast in optically detected magnetic resonance readout and improved signal to noise ratio. Thus, our experimental results supported by simulations, constitute a first step towards integration of hBN spin defects with photonic resonators for a scalable spin-photon interface.

We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality.

Knowledge concerning the sintering behavior of gold nanoparticles (AuNPs) allows for improved nanomaterials for applications such as printed electronics, catalysis and sensing. In this study, we examined the ability of a range of compounds to stabilize AuNPs against thermal sintering and compared compounds with and without functional groups that anchor the molecules to the nanoparticle surface. Thermal stability was characterized in terms of the temperature of the sintering event (TSE) as well as thermogravimetric analysis and scanning electron microscopy. We show that anchored stabilizing compounds with high thermal stability are effective at preventing the sintering of AuNPs until the decomposition of the compound. A TSE of 390 °C was achieved using 1pyrenebutanethiol as stabilizer. Of the unanchored stabilizers, which were combined with butanethiol-capped AuNPs, two were found to be particularly effective: oleylamine (TSE ≈ 300 °C) and a perylenedicarboximide derivative (TSE ≈ 540 °C), the latter conferring an unprecedented level of thermal stability on ligand-stabilized AuNPs. When selecting stabilizers without anchoring groups, our results demonstrate the importance of choosing those that have an affinity with the capping ligands on the AuNPs to ensure a uniform mixture of AuNPs and stabilizer within a film.