Photophysics and Applications of Spin Defects in Hexagonal Boron Nitride
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2025-01-01 |
| Journal | RMIT |
| Authors | Robertson, Islay |
| Institutions | MIT University, RMIT University |
Abstract
Section titled āAbstractāOptically addressable spin defects in solid-state material are renowned as robust platforms for the development of quantum technology applications and studying quantum phenomena at room temperature. Until recently, these defects had only been studied in bulk-like 3D crystal hosts such as diamond and silicon carbide, which stabilise their spin properties creating ideal conditions for robust quantum devices. Quantum sensing in particular has driven the development and optimisation of the host material and defect though some applications have been limited by integrability of the bulk-like 3D crystal and the poor stability of near surface defects. Isolation of freestanding single crystal sheets from layered van der Waals (vdW) materials by exfoliation has shown the potential of 2D materials for simple, fully integrated devices on the atomically thin scale. Spin defects in 2D materials have subsequently become of interest for the development of quantum sensing technologies. The thesis at hand starts after the recent discovery of the negatively charged boron vacancy defect and subsequent initial demonstrations of quantum sensing, as well as the isolation of single spin-active carbon emitters in hexagonal boron nitride (hBN). Chapter 1 will review current understanding of spin defects in hBN, using the history of their bulk-like 3D crystal hosted predecessors as a backdrop to motivate their application towards quantum sensing. Then in Chapter 2 we assess the viability of the boron vacancy defect for the detection of paramagnetic ions using spin relaxometry, leveraging the near atomic proximity between the spin defect and the sensing target as enabled by the vdW nature of hBN. As a part of this chapter we identify shortcomings of the boron vacancy defect which we use as motivation for the importance of focusing our efforts on the carbon emitters. However, as there is little consensus on the origins of the carbon emitters spin properties, in Chapter 3 we focus on reconciling a photodynamic model to explain optically detected magnetic resonance (ODMR) with a microscopic model for the defect structure. We identify anomalous spin properties to arise from a weakly coupled spin pair system and attribute ODMR to a general charge transfer mechanism which may be extended to other defect systems in materials other than hBN. Finally, with our newfound understanding of the carbon emitters, in Chapter 4 we take advantage of their unique spin properties and demonstrate a simple radiofrequency analysis device.