Diamond-defect engineering of NV− centers using ion beam irradiation

• Published in: Diamond and related materials 2025-01, Vol.151, Article 111838
• Main Authors: Sánchez Toural, J.L., García-Pérez, J., Bernardo-Gavito, R., Granados, D., Andrino-Gómez, A., García, G., Pau, J.L., Ramos, M.A., Gordillo, N.
• Format: Article
• Language: English
• Subjects: Diamond; Ion-beam irradiation; Nitrogen vacancy; NV- colour centers; Quantum sensing
• ISSN: 0925-9635
• DOI: 10.1016/j.diamond.2024.111838

The interplay between ion beam modification techniques in the MeV range and the controlled generation of negatively charged nitrogen-vacancy (NV−) centers in nitrogen-doped synthetic diamond crystals is explored. An experimental approach employing both light (H+) and heavy (Br+6) ions was followed to assess their respective impacts on the creation of NV− centers, using different ion energies or fluences to generate varying amounts of vacancies. Photoluminescence spectroscopy was applied to characterize NV− and neutral NV0 centers. Initially, no NV centers were detected post-irradiation, despite the presence of substitutional nitrogen and vacancies. However, after annealing at 800 °C (and in some cases at 900 °C), most samples exhibited a high density of NV0 and especially NV− centers. This demonstrates that thermal treatment is essential for vacancy‑nitrogen recombination and NV− formation, often through electron capture from nearby nitrogen atoms. Notably, we achieved high NV− densities without graphitization, which is essential for preserving the material's properties for quantum applications. This study underscores and quantifies the effectiveness of MeV-range ions in controlling vacancy distributions and highlights their potential for optimizing NV− center formation to enhance the sensitivity of diamond-based quantum magnetic sensors. [Display omitted] •MeV-range ion irradiation was used to control the generation of NV− centers in nitrogen-doped synthetic diamond crystals, employing both light (H+) and heavy (Br+6) ions.•Vacancy concentrations were precisely tailored by adjusting ion energies and fluences, leading to varying amounts of vacancies, but no NV centers were initially detected after irradiation.•Thermal annealing at 800 and 900 °C was crucial for enabling the recombination of vacancies and nitrogen atoms, resulting in the formation of NV− centers.•High conversion rates and NV− densities were achieved post-annealing, without inducing graphitization, which is important for maintaining the material's quality.•Optimized NV− center formation using MeV ions highlights their potential for enhancing the sensitivity of diamond-based quantum magnetic sensors.