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A cost‐effective approach to provide diamond platelets containing nitrogen vacancy center ensembles (NVs) in the range of ppm is investigated. Industry‐type high‐pressure–high‐temperature‐diamond type 1b containing a high number of interstitial nitrogen in the range of several tens of ppm are used and small diamond platelets (size ≈1 × 1 mm 2 , thickness ≈300 μm) are prepared by laser cutting and polishing. The nitrogen is converted into NV by means of high‐energy electron irradiation of 10 MeV and annealing at 900 °C. Variations in the irradiation dose between 0.5E18 1/cm 2 and 2E18 1/cm 2 result in different densities of NV. The diamond platelets are analyzed with regard to their nitrogen concentration and photoluminescence as well as optically detected magnetic resonance is used to investigate the usability for a NV‐based magnetometer. A method to calculate the ratio of negatively to neutrally charged NV (NV − /NV 0 ) is proposed that uses the photoluminescence intensities of the spectrum at 575 and 638 nm, namely, the zero‐phonon lines of NV − and NV 0 .
Bähr et al. (Sun,) studied this question.