On the Formation of Dense Arrays of Nitrogen–Vacancy Centers in Synthetic Single-Crystal Diamonds for Quantum Sensors

The dynamics of the formation of ensembles of nitrogen–vacancy color centers (NV centers) in single-crystal diamond plates after irradiation by high-energy (2 MeV) electrons and subsequent annealing is investigated. The concentration of the nitrogen impurity is determined from the infrared (IR) absorption spectrum to be 90 and 4 ppm for the diamond growth sectors 111 and 001, respectively. The transverse relaxation times T_2^* for the electron spin of NV centers are studied; they are found to amount to 200 and 900 ns for the 111 and 001 sectors, respectively, and are limited by the concentration of paramagnetic impurity defects in diamond. The sensitivity of quantum sensors based on the obtained ensembles of NV centers is estimated; the estimation shows feasibility of using denser ensembles in low-field magnetometry.