Spin properties of NV ensembles in phosphorus doped diamond
Résumé
Nitrogen-vacancy (NV) color centers in diamond have demonstrated their full potential in various applications, ranging from highly-sensitive nanoscale magnetometers [1], high-pressure sensors [2] and diamond-based quantum applications [3]. As a solid-state spin, the properties of these color centers strongly depend on the host material. Recent works nicely demonstrated this point: isotopic purification has shown to improve the spin coherence time of low impurity concentration diamond [4], while phosphorous doping allows to improve NV charge stability [5] and lead to record spin coherence [6]. In this work, we investigate the spin properties of native NV ensembles in phosphorus-doped diamond layers, homoepitaxially grown on (100) Ib HPHT substrates with either natural or isotopically purified methane. The concentrations of phosphorus, nitrogen and NV centers, [P], [N] and [NV], are quantified by different techniques including SIMS, absorption and photoluminescence (PL) at low temperature. First, low temperature PL confirms phosphorus doping (7x1013 – 7x1015 P.cm-3) stabilizes the negative charge state of the NV center with a NV0 population that remains below 10% even at 1 mW laser power. Then, the dephasing time of spin ensemble (T2*) is characterized by Optical Detected Magnetic Resonance (ODMR) under continuous excitation. We investigate the T2* dependence with [N], which is the majority impurity in the samples. We found results that are consistent with a dipolar coupling of NVs with a bath spins made of nuclear 13C and/or substitutional nitrogen. We found T2* around 0.5 μs for natural isotopic composition, and up to ~3 μs for 12C purified diamond with [N] = 6.3x1016 cm-3. These results are promising for diamond quantum magnetometers with NV centers. References 1. G. Balasubramanian, et al. Nature 455 (2008), 7213. 2. M. Lesik, et al. Science 366 (2019), 6471. 3. L. Childress et al. Science 314 (2006), 5797. 4. G. Balasubramanian et al. Nature Materials 8 (2009), 383. 5. Y. Doi et al. Physical Review B 93 (2016), 081203. 6. E.D. Herbschleb, et al. Nature Communications 10 (2019), 3766.
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