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We report on an ion implantation technique utilizing a screening mask made of SiO2 to control both the depth profile and the dose. By appropriately selecting the thickness of the screening layer, this method fully suppresses the ion channeling, brings the location of the highest nitrogen-vacancy (NV) density to the surface, and effectively reduces the dose by more than three orders of magnitude. With a standard ion implantation system operating at the energy of 10 keV and the dose of 1011 cm² and without an additional etching process, we create single NV centers close to the surface with coherence times of a few tens of µs. [ABSTRACT FROM AUTHOR]

We perform pulsed optically detected electron spin resonance to measure the DC magnetic field sensitivity and electronic spin coherence time T2 of an ensemble of near-surface, high-density nitrogen-vacancy centers engineered to have a narrow magnetic resonance linewidth. Combining pulsed spectroscopy with dynamic nuclear polarization, we obtain the photon-shot-noise-limited DC magnetic sensitivity of 35 nT Hz-0.5. We find that T2 is controlled by instantaneous diffusion, enabling decoherence spectroscopy on residual nitrogen impurity spins in the diamond lattice and a quantitative determination of their density. The demonstrated high DC magnetic sensitivity and decoherence spectroscopy are expected to broaden the application range for two-dimensional magnetic imaging. [ABSTRACT FROM AUTHOR]

We report on a microwave planar ring antenna specifically designed for optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in diamond. It has the resonance frequency at around 2.87 GHz with the bandwidth of 400 MHz, ensuring that ODMR can be observed under external magnetic fields up to 100 G without the need of adjustment of the resonance frequency. It is also spatially uniform within the 1-mm-diameter center hole, enabling the magnetic-field imaging in the wide spatial range. These features facilitate the experiments on quantum sensing and imaging using NV centers at room temperature. [ABSTRACT FROM AUTHOR]