Robust multicolor single photon emission from point defects in hexagonal boron nitride (1603.09608v1)

Abstract: Hexagonal 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.

• The paper demonstrates that robust multicolor single-photon emission from hBN defects can be reliably engineered using localized electron beam irradiation and high-temperature annealing.
• The paper categorizes emitters into two groups based on their zero-phonon line and phonon sideband features, revealing differences in spectral range and stability.
• The paper shows that hBN emitters exhibit short lifetimes and resilient photophysical properties, underlining their potential for scalable quantum photonics applications.

An Analysis of Multicolor Single Photon Emission from Point Defects in Hexagonal Boron Nitride

This paper presents a thorough investigation into the multicolor single photon emission characteristics of point defects in hexagonal boron nitride (hBN) multilayers, establishing the substance as a promising candidate for quantum photonics at room temperature. The research delineates key photophysical properties and provides an in-depth analysis of the approaches to engineering emitters, highlighting the robust nature of these defects under various conditions.

Key Findings and Methodologies

The authors categorize the photon emitters in hBN into two primary groups based on their zero-phonon line (ZPL) energy and phonon side band (PSB) spectral characteristics. Group 1 emitters tend to have a wide spectral range with asymmetric ZPLs, while Group 2 emitters exhibit narrower and more symmetric ZPLs. The presence of pronounced phonon sidebands in Group 1 also distinguishes it from Group 2. These distinctions are supported by detailed photoluminescence (PL) measurements performed at room temperature, showing that the ZPL spans a wide spectral range over 200 nm.

Two distinct methodologies are delineated for the engineering of these emitters: electron beam irradiation and high-temperature annealing in inert and reactive gaseous environments. Both methods successfully produce stable and bright single photon emitters. Notably, the electron beam irradiation method allows for localized defect generation without requiring high-temperature annealing. The paper provides rigorous analysis of these methodologies, emphasizing their adaptability and robustness for producing stable defects.

The stability of the emitters was tested through sequential annealing in different environments (e.g., hydrogen, oxygen, and ammonia), demonstrating remarkable robustness. These experiments suggest that the emitters likely have vacancy-related defects in their crystallographic structure and are likely charge-neutral, as their emission characteristics remained unchanged across different treatments.

Photophysical Properties and Implications

Photophysical characterization reinforced the superior properties of the emitted light. The emitters exhibit short lifetimes (2.9 and 6.7 ns for representative emitters), and their emission rates saturate at specific excitation powers. Temporal analysis of photon antibunching elucidated the presence of metastable states, which differ significantly between the two groups, accounting for variations in brightness and emission stability.

The paper suggests that local environmental factors such as strain and dielectric surroundings significantly impact the emitters' photophysical behavior, evident from the observed variations in ZPL energy within each group. Density Functional Theory (DFT) simulations further corroborate the strain-induced shifts in optical transitions.

Theoretical and Practical Implications

This research lays foundational understanding for using hBN in quantum photonic applications, leveraging the stability and room temperature operability of multicolor single-photon emission. The robust methodologies for creating these emitters enhance prospects for integrating hBN into nanophotonic devices and quantum information processing systems. The evident resilience of these emitters to environmental changes also suggests their potential use in hostile conditions, possibly extending to sensing applications at the nanoscale.

Future Directions

Future research may focus on refining the control over the defect engineering process to achieve homogeneous distributions of emitter properties, thereby increasing the efficacy of potential applications. Additionally, further exploration into the theoretical modeling of the interaction between local environments and defect characteristics could provide greater insights into tuning emitter properties for specific applications.

Overall, the paper significantly advances the knowledge of multicolor single-photon emission in planar materials, promoting further exploration into the integration of two-dimensional materials into cutting-edge quantum technologies.