Enhancing quantum sensing performance by optimizing the concentration and dephasing time of the NV ensemble in CVD-diamond

The negatively charged nitrogen-vacancy (NV^-) center ensembles in diamonds offer enormous potential for developing integrated sensors with an improved signal-to-noise ratio (SNR) and high sensitivity. However, the preparation and treatment of diamond samples with suitable NV^- concentrations and dephasing time have remained challenging. This work provided insight into the NV^- center formation mechanism and reconstruction via a comprehensive analysis of the concentration and dephasing time of a set of diamond samples treated by various parameters. By varying the electron irradiation dose and subsequent annealing duration, the conversion rate of nitrogen to NV^- is up to 18.45%, and the corresponding maximum NV^- concentration is 3.69 ppm. The dephasing time for all samples varies around 300 ns. The nitrogen-related NV^- center ensemble dephasing rate per unit density is 146.4 (ppm·ms)^-1, indicating that the treatment did not substantially alter the paramagnetic spin environment around the NV^- center. This study not only offers support to exquisite sensitivities of NV-based sensors but also provides valuable experience for the preparation of unique properties of synthetic diamonds.