An efficient method to create high-density nitrogen-vacancy centers in CVD diamond for sensing applications

The negatively charged Nitrogen-Vacancy (NV-) center in diamond is one of the most versatile and robust quantum sensors suitable for quantum technologies, including magnetic field and temperature sensors. For precision sensing applications, densely packed NV- centers within a small volume are preferable due to benefiting from 1/root N sensitivity enhancement (N is the number of sensing NV centers) and efficient excitation of NV centers. However, methods for quickly and efficiently forming high concentrations of NV- centers are in the development stage. We report an efficient method for creating high-density NV- centers production from a relatively low nitrogen concentration based on high-energy photons generated from Ar+ plasma source. This study was done on type-IIa, single crystal, chemical vapor deposition (CVD)-grown diamond substrates with an as-grown nitrogen concentration of 1 x 10(17) cm(-3). We created high NV- density (similar to 20,000 NVs over the diffraction limited sample volume) distributed homogeneously over 150-200 mu m deep from the diamond surface. The plasma-created NV-s in CVD diamond have a spin-lattice relaxation time (T1) of 5 ms and a spin-spin coherence time (T2) of 4 mu s. We measure a DC magnetic field sensitivity of -104 nT Hz(-1/2), an AC magnetic field sensitivity of ~ 0.12 pT Hz(-1/2) and demonstrate real-time magnetic field sensing at a rate over 10 mT s(-1) using the diffraction limited sample volume.