Fig. 3: Electron spin properties of NV⁻ centers formed by SHIs characterized by ODMR.

a A comparison of ESR signal of the electron spin state m_s = +1 of the NV⁻ centers probed in the area with (black dots) and without (blue dots) SHI irradiation after thermal annealing, with the external magnetic field of 80 Gauss was aligned to the  < 001 > crystallographic orientation. Red curves correspond to the single Gaussian fitted individual resonance, with an extracted FWHM of the ESR signal of 13.9 ± 0.1 MHz and 14.4 ± 0.2 MHz probed in the area with and without SHI irradiation, respectively; b The correspondent Rabi oscillations contrast of NV⁻ spins probed in the SHI irradiated area of sample B after thermal annealing. Red curve correspond to the sinusoidal function modulated by single exponential decay, with an extracted Rabi dephasing time of 0.53 ± 0.04 μs; c Presents the correspondent T1 relaxation contrast of NV⁻ spins probed in the SHI-irradiated area of sample B after thermal annealing, by using a 200 ns π pulse calibrated by the Rabi oscillation. Red curve correspond to single exponential decay, with extracted T1 coherent time of 5.8 ± 0.2 ms; d Presents the T2 relaxation contrast of NV⁻ spins probed in the SHI-irradiated area of sample B after thermal annealing, by implementing spin echo (Hahn-echo) MW pulse sequence. Red curve correspond to the fit by the model referred to ref. ⁴⁶, which allows to extract the T2 coherent time of 48.1 ± 9.7 μs and T2^* time of 2.4 ± 0.2 μs.