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Defects introduced to synthetic type Ib diamond micrometer-size particles by electron-beam irradiation were studied by electron paramagnetic resonance and photoluminescence (PL) spectroscopy as a function of e-beam fluence and post-irradiation thermal annealing. Increasing electron-beam fluence causes a substantial reduction of the substitutional nitrogen (P1) content, accompanied by progressively higher concentrations of paramagnetic negatively charged vacancies (V−) and triplet interstitials (R1/R2). Annealing results in a drastic decrease in the V− and R1/R2 content and an increase in the negatively charged nitrogen-vacancies (NV− or W15). Analysis of PL spectra allows for identification of color centers in the irradiated diamond samples and following their evolution after annealing. These data facilitate understanding of different factors contributing to the formation of color centers in diamond and promote efforts toward controlled engineering of optical centers in fluorescent diamond particles. [ABSTRACT FROM AUTHOR]

Fluorescent color centers in diamond are invaluable room temperature quantum systems in fundamental scientific studies and vital for many emerging applications from inertial navigation to quantum sensing in biology. Yet, controlled production of specific color centers in synthetic diamond at scale remains challenging. Characteristics of silicon‐ and nickel‐based defects with strong fluorescence in the 700–950 nm spectral region formed in Si‐ and Ni‐doped diamond, created via high‐pressure high‐temperature synthesis in commercial quantities without irradiation, are reported. Using electron paramagnetic resonance spectroscopy and fluorescence spectroscopy, the presence of defects including the negatively charged silicon‐vacancy (SiV−), silicon‐boron (SiB) and positively charged substitutional nickel center (Nis+) in micrometer‐sized particles is identified and quantified. The color centers' optical properties are investigated via time‐resolved and steady‐state fluorescence spectroscopy below 10 K and at room temperature. In ensemble measurements, the particles show no detectable signals from nitrogen‐vacancy (NV−) defects. The particles' relative fluorescence brightness is quantified and compared to particles containing ≈1 ppm NV− centers. It is demonstrated that the Nis+ center fluorescence characteristics are preserved in 50 nm nanoparticles. The work paves the way for the use of fluorescent nanodiamonds in the first near‐infrared biological window between 700 nm and 950 nm in biomedical applications. [ABSTRACT FROM AUTHOR]

Enhancement of X‐ray excited optical luminescence in a 100 µm‐thick diamond plate by introduction of defect states via electron beam irradiation and subsequent high‐temperature annealing is demonstrated. The resulting X‐ray transmission‐mode scintillator features a linear response to incident photon flux in the range 7.6 × 108 to 1.26 × 1012 photons s−1 mm−2 for hard X‐rays (15.9 keV) using exposure times from 0.01 to 5 s. These characteristics enable a real‐time transmission‐mode imaging of X‐ray photon flux density without disruption of X‐ray instrument operation. [ABSTRACT FROM AUTHOR]

The article studies negatively charged nitrogen-vacancy (NV) centers in diamond and its importance in the field of medical and geological exploration. It discusses that best magnetic field sensitivities are reached by superconducting quantum interference devices (SQUIDs) and vapor cells; to achieve strong stimulated emission pumping of a high number of NV centers is needed, demonstration of strong light amplification, to investigate the magnetic field dependency of the measured amplification.

Recent advancements in high temperature rapid thermal annealing (RTA) of irradiated diamond particles has made possible the production of the particles with fluorescence based on complexes of nitrogen and vacancies in a broad range of colors: blue, green, red/NIR as well as their mixtures, depending on the temperature and irradiation fluence. Still, the production of fluorescent diamond particles suffers from fluorescence inhomogeneity among particles. The goal of the current study is improvement of the fluorescence uniformity among the treated particles. Experiments were performed using as-grown 40 μm in diameter type Ib synthetic diamond particulate assuming that nitrogen uniformity among the as-grown particles should be higher versus milled ones used in previous studies. Particles were irradiated under mild conditions with 1 MeV electrons to a fluence 3 × 1018 e/cm2 without overheating during irradiation which resulted in relatively uniform green fluorescence among particles treated via RTA at temperatures corresponding to H3 centers formation. [ABSTRACT FROM AUTHOR]