Efficient Conversion of Nitrogen to Nitrogen-Vacancy Centers in Diamond Particles with High-Temperature Electron Irradiation

TL;DR

This study demonstrates a high-yield method for converting nitrogen to nitrogen-vacancy centers in diamond particles using high-temperature electron irradiation, enhancing their potential for sensing and biomedical applications.

Contribution

The paper introduces a novel high-energy electron irradiation technique combined with annealing to efficiently produce NV$^-$ centers with up to 25% conversion yield in diamond particles.

Findings

Achieved up to 25% conversion yield of NV$^-$ centers.

Characterized irradiation-induced spin defects W16 and W33.

Investigated effects of irradiation dose and particle size on NV coherence times.

Abstract

Fluorescent nanodiamonds containing negatively-charged nitrogen-vacancy (NV$^-$) centers are promising for a wide range of applications, such as for sensing, as fluorescence biomarkers, or to hyperpolarize nuclear spins. NV$^-$ centers are formed from substitutional nitrogen (P1 centers) defects and vacancies in the diamond lattice. Maximizing the concentration of NVs is most beneficial, which justifies the search for methods with a high yield of conversion from P1 to NV$^-$. We report here the characterization of surface cleaned fluorescent micro- and nanodiamonds, obtained by irradiation of commercial diamond powder with high-energy (10 MeV) electrons and simultaneous annealing at 800{\deg}C. Using this technique and increasing the irradiation dose, we demonstrate the creation of NV$^-$ with up to 25 % conversion yield. Finally, we monitor the creation of irradiation-induced spin-1 defects in microdiamond particles, which we associate with W16 and W33 centers, and investigate the effects of irradiation dose and particle size on the coherence time of NV$^-$.