Optimizing the density of nitrogen implantation for generating high-density NV center ensembles for quantum sensing

We prepared four NV center ensembles with different nitrogen atom doses at the same diamond by ion implantation. The densities of NV centers in the samples were analyzed using their fluorescence intensities and PL spectra, which increases with the implantation dose and reaches a maximal value at a dose of 1014  cm−2 , corresponding to the nitrogen density of 3.1 × 1019  cm−3 . Ramsey measurement showed that no significant difference was found in the dephasing time between the four NV − center ensembles. The results suggest that the quantum sensor utilizing NV − ensemble centers can achieve its best sensitivity when the density of nitrogen atoms in diamond is about 3.1 × 1019  cm−3 .