Optimisation of electron irradiation for creating spin ensembles in hexagonal boron nitride

TL;DR

This study systematically optimizes electron irradiation doses in hexagonal boron nitride to enhance the creation of boron vacancy centers, improving the scalability and sensitivity of quantum sensors.

Contribution

It provides the first detailed analysis of electron irradiation parameters for defect creation in bulk hBN, highlighting optimal doses and the influence of crystal purity.

Findings

Moderate electron doses (~5×10^{18} cm^{-2}) yield the best measurement sensitivity.

Initial crystal purity affects defect creation efficiency.

Results enable scalable production of hBN quantum sensors.

Abstract

Boron vacancy centre ($V_{\rm B}^-$) ensembles in hexagonal boron nitride (hBN) have attracted recent interest for their potential as two-dimensional solid-state quantum sensors. Irradiation is necessary for $V_{\rm B}^-$ creation, however, to date only limited attention has been given to optimising the defect production process, especially in the case of bulk irradiation with high-energy particles, which offers scalability through the potential for creating ensembles in large volumes of material. Here we systematically investigate the effect of electron irradiation by varying the dose delivered to a range of hBN samples, which differ in their purity, and search for an optimum in measurement sensitivity. We find that moderate electron irradiation doses ($\approx 5\times 10^{18}$~cm$^{-2}$) appear to offer the best sensitivity, and also observe a dependence on the initial crystal purity. These results pave the way for the scalable and cost-effective production of hBN quantum sensors, and provide insight into the mechanisms limiting $V_{\rm B}^-$ spin properties.