Structural attributes and photo-dynamics of visible spectrum quantum emitters in hexagonal boron nitride

Abstract: Newly discovered van der Waals materials like MoS$_2$, WSe$_2$, hexagonal boron nitride (h-BN), and recently $\mathrm{C}_2\mathrm{N}$ have sparked intensive research to unveil the quantum behavior associated with their 2D structure. Of great interest are 2D materials that host single quantum emitters. h-BN, with a band gap of 5.95 eV, has been shown to host single quantum emitters which are stable at room temperature in the UV and visible spectral range. In this paper we investigate correlations between h-BN structural features and emitter location from bulk down to the monolayer at room temperature. We demonstrate that chemical etching and ion irradiation can generate emitters in h-BN. We analyze the emitters' spectral features and show that they are dominated by the interaction of their electronic transition with a single Raman active mode of h-BN. Photodynamics analysis reveals diverse rates between the electronic states of the emitter. The emitters show excellent photo stability even under ambient conditions and in monolayers. Comparing the excitation polarization between different emitters unveils a connection between defect orientation and the h-BN hexagonal structure. The sharp spectral features, color diversity, room-temperature stability, long-lived metastable states, ease of fabrication, proximity of the emitters to the environment, outstanding chemical stability, and biocompatibility of h-BN provide a completely new class of systems that can be used for sensing and quantum photonics applications.

Structural Attributes and Photo-Dynamics of Visible Spectrum Quantum Emitters in Hexagonal Boron Nitride

The study explores the interactions between structural characteristics and photo-dynamics of visible spectrum quantum emitters (QEs) within hexagonal boron nitride (h-BN). The investigation delves into the potential of h-BN as a host for stable single quantum emitters (SQEs) across UV and visible spectral ranges, focusing on the correlation between its structural features and emitter location from bulk to mono-layer, under ambient conditions. This research is crucial for advancing quantum photonics applications due to the biocompatibility, outstanding chemical stability, and ease of fabricating h-BN-based systems.

Key Findings

The primary contributions of the study manifest in the following:

1. Emission and Polarity Characteristics: The researchers provide evidence of the connection between the defect orientation and h-BN’s hexagonal structure, through comparative analyses of excitation polarization. They illuminate the influences of emitters' photo-stability and their diverse electronic transition rates.

2. Methods for Quantum Emitter Creation: Two primary methods—chemical etching and ion irradiation—are employed to generate emitters in h-BN. Chemical methods incorporated the use of peroxymonosulfuric acid among others, while ion irradiation involved the use of helium (He) and nitrogen (N) ions to induce emission-friendly defects.

3. Spectral Characteristics and Stability: The emitters exhibited prominent sharp spectral features and long-lived meta-stable states. Spectral analyses of the QEs revealed emission dominated by the interaction of the electronic transition with a h-BN Raman active mode, identifiable through well-characterized Raman harmonic structures.

Implications and Future Prospects

Theoretical Implications: The study suggests that the reduced dimensionality of h-BN significantly influences SQEs' positional and transition rate behavior, aligning with observations from three-dimensional materials like diamond. This is supplementary to theoretical models predicting noticeable interactions between electronic and phonon modes within low-dimensional materials.

Practical Implications: From a practical standpoint, the findings underscore the potential for h-BN emitters in developing quantum photonic devices. This includes their integration into optical nanosensors due to their emission stability and broad spectral range.

Speculation on Future Developments: The reported research can pioneer advancements in two-dimensional quantum emitters, where enhanced understanding and manipulation of defect structures open avenues for tailored optoelectronic devices. The demonstrated defect engineering methods could be refined for precise applications in quantum information science and nanophotonics.

In conclusion, while the study does not claim extensive breakthroughs, it provides substantial insights and methodologies with implications for ongoing and future research into h-BN and similar materials. The characterization techniques, combined with the tuning of material properties, offer fertile ground for the development of versatile quantum optical components. Enhancing the understanding of SQEs in 2D materials can cement their role in the next generation of photonic and quantum devices.