The study of the efficiency of nitrogen to NV-center conversion in high nitrogen content samples

The nitrogen-vacancy color center in diamond is one of the most important systems in the fast-growing field of sensing. This color centers are used in both high-resolution and high-sensitivity sensors. However, techniques for quick and efficient formations of this color center are still in the development stage. In this paper, we present a study on the influence of the electron irradiation dose on the conversion of substitutional nitrogen into $\text{N}{{\text{V}}^{-}}$ centers. The study was done on diamonds that were highly enriched with nitrogen (~100 ppm), which on one hand should maximize the effect of irradiation, and on another be of interest for high-sensitivity magnetometers. The maximum achieved conversion efficiency was as high as ${37\pm 3.7}$, with no observed saturation on the electron dose even with the simplest annealing procedure. The measurements of the corresponding dephasing time made it possible to estimate for shot-noise limited sensitivity per unit volume of a stationary field sensor with such a diamond to be ${9\pm 1\times {{10}^{-14}}\text{T}}/{\sqrt{\text{Hz}\cdot \text{m}{{\text{m}}^{-3}}}}\;$.