Creating high-density NV^- centers in CVD diamond using high-energy photons from Ar⁺ plasma

High-density Nitrogen-Vacancy (NV) centers in diamond are among the most versatile quantum sensors used in many sensing applications, including magnetic field sensors [1]. The existing methods to create, such as high-density NV^- centers, are expensive and cumbersome, often requiring a large dose of nitrogen implantation, degrading the quantum properties. The methods for the quick and efficient creation of NV^- centers are still developing. In this talk, we present a novel and cost-effective approach to creating high-density NV- centers in a single crystal, CVD-grown diamond substrate with as-grown Nitrogen concentration < 1 ppm. We create a high-density NV^- center by exposing the diamond substrate in Ar+ plasma for 30 s [2] followed by two hours of thermal annealing at 1100 ^oC. Based on optically detected magnetic resonance and fluorescence microscopy measurements, we estimate an NV^- density of ~10¹⁵ cm^-3 (~0.02 ppm), a four-fold higher than as-grown NV^- concentration, distributed homogeneously over 200 um depth from the diamond surface. The created NVs have spin-lattice relaxation time (T₁) of 5 ms and a spin-spin coherence time (T₂) of 4 us. We measure a DC magnetic field sensetivity ~108 nT/ Hz^1/2 using a sample volume of 0.2 um³. [1] V. M Acosta, et al., Phys. Rev. B 80 115202 (2009), [2] K. Ambal, et al., Phys. Rev. Applied 4, 024008 (2015).