(4cn) Towards Practical Quantum Applications Via Defect Engineering in Two-Dimensional Materials

Single-photon emitters (SPEs) are essential building blocks in photonic quantum technologies. Hexagonal boron nitride (hBN) is emerging as a promising two-dimensional (2D) material that can host bright, room-temperature SPEs. Emitting defects in hBN exhibit a wide range of emission energies, but identifying the properties and origins of specific emitters remains challenging, which is confounded by the exponential scaling of potential candidates with the number of lattice atoms removed. To address this challenge, we collect more than 2000 spectra consisting of single, isolated zero-phonon lines in the visible range, and observe that most of them are organized into 6 discretized emission energies. We then develop facile, scalable chemical processing schemes that generate or interconvert specific emitters, respectively. The identification and chemical interconversion of these discretized emitters should significantly advance our understanding of the solid-state chemistry and photophysics of hBN defects.

The promise of utilizing these emitting defects for practical applications can be seriously limited by commonly observed photobleaching. We present a systematic study comparing diverse hBN samples in a controlled atmospheric environment. Independent of the source or the number of layers of hBN, we find that the photobleaching of a common emission at 1.98 ± 0.05 eV can be described by two consistent time constants. Only the former is environmentally sensitive, and can be mitigated by shielding oxygen, whereas the latter is the result of carbon-assisted defect migration. We further colocalize the photobleaching experiment with scanning transmission electron microscopy, and present a rich variety of atomic-scale defect structures in hBN with unprecedented crystallographic details. Our findings reveal a key to photostable luminescence in hBN, and provide new insight into the structural origins of hBN quantum emission.

Research Interests: Harnessing the laws of quantum mechanics for real-world applications has emerged as one of the most intriguing and rapidly growing research fields in recent years. Quantum systems are extremely sensitive to environmental disturbance, which leads to main challenges for certain applications such as quantum computing and cryptography. This unprecedented level of sensitivity, however, could well become an advantage and be exploited in sensing. In particular, photon-based quantum sensing platforms are very appealing, with the potential of integrating with many existing optical characterization tools, and compatible with chemical and biological systems. My research interest lies in 1) exploring new quantum materials with scalable synthesis routes and facile modulation methods, with a particular emphasis on defect engineering in 2D materials; 2) constructing room-temperature quantum sensing schemes that exploit these new material systems, which should be compatible with biochemical systems; 3) utilizing quantum sensing platforms to study ion transport and cell signaling in a fluidic environment.

Teaching Interests: Physics, Nanotechnology, Differential Equations