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arXiv · 2510.13991

Impact of irradiation conditions on the magnetic field sensitivity of spin defects in hBN nano flakes

Saksham Mahajan·Ravi Kumar·Aferdita Xhameni·Gautham Venu·Basanta Mistri·Felix Donaldson·T. Taniguchi·K. Watanabe·Siddharth Dhomkar·Antonio Lombardo·John J. L. Morton
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Abstract

We study $V_{\mathrm{B}}^-$ centres generated by helium focused ion beam (FIB) irradiation in thin ($\sim$70 nm) hBN nanoflakes, in order to investigate the effect of implantation conditions on the key parameters that influence the magnetic field sensitivity of $V_{\mathrm{B}}^-$ quantum sensors. Using a combination of photoluminescence, optically detected magnetic resonance, and Raman spectroscopy, we examine the competing factors of maximising signal intensity through larger $V_{\mathrm{B}}^-$ concentration against the degradation in spin coherence and lattice quality observed at high ion fluences. Our results indicate that both the $V_{\mathrm{B}}^-$ spin properties and hBN lattice parameters are largely preserved up to an ion fluence of $10^{14}$ ions/cm$^2$, and beyond this significant degradation occurs in both. At the optimal implantation dose, an AC magnetic sensitivity of $\sim 1\,μ\mathrm{T}/\sqrt{\mathrm{Hz}}$ is achieved. Using the patterned implantation enabled by the FIB, we find that $V_{\mathrm{B}}^-$ centres and the associated lattice damage are well localised to the implanted regions. This work demonstrates how careful selection of fabrication parameters can be used to optimise the properties of $V_{\mathrm{B}}^-$ centres in hBN, supporting their application as quantum sensors based on 2D materials.

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Saksham Mahajan, Ravi Kumar, Aferdita Xhameni, Gautham Venu, Basanta Mistri, Felix Donaldson, T. Taniguchi, K. Watanabe, Siddharth Dhomkar, Antonio Lombardo, John J. L. Morton. 2025-10-15. Impact of irradiation conditions on the magnetic field sensitivity of spin defects in hBN nano flakes. https://arxiv.org/abs/2510.13991

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