Nitrogen concentration control in diamond crystal growth for quantum sensing applications

T. Teraji, C. Shinei, Masuyama Yuta, M. Miyakawa, T. Taniguchi

Published Sep 12, 2023• 0 citations

Abstract

To improve the sensitivity of magnetic sensors using negatively charged nitrogen-vacancy (NV−) centers, it is essential to improve the quality of diamond crystals and precisely control the nitrogen concentration in the crystals. We have utilized high-pressure, high-temperature synthesis [1] and chemical vapor deposition [2] for the growth of nitrogen-doped diamond. The concentration of substitutional nitrogen in the neutral charge state [NS0] were evaluated by electron paramagnetic resonance (EPR) measurements. As shown in Fig. 1, [NS0] were precisely controlled by the weight ratio of nitrogen getter material in the metal solvent for the HPHT method (Fig. 1(a)) and by the carbon to nitrogen gas ratio for the CVD method (Fig. 1(b)). Then, the diamond crystals were irradiated with electron beams followed by vacuum annealing so that 10% of the nitrogen at the substitutional site became NV− centers, and the negatively charged NV− centers were successfully formed preferentially [3]. T2 of these diamond crystals was inversely proportional to the nitrogen concentration. The product of T2 and nitrogen concentration of the obtained HPHT diamond crystal is slightly higher than the maximum value reported so far [4], suggesting that the crystal is expected to have high magnetic sensitivity.

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