A crystal growth technique enabling to control the depth of a single nitro\-gen-vacancy (NV) center at nanometer scale in diamond is developed. This nitrogen delta-doping technique during the plasma-enhanced chemical vapor deposition (PE-CVD) of diamond enables to create near-surface NV centers whose depths ranging from about 100 nm down to less than 2 nm while preserving their spin coherence times.

These shallowly doped, long-coherence NV centers are used as an atomic-scale magnetic sensor that enables to detect nuclear spin signal from an organic sample of a nanometer-scale volume {\it external} to the diamond crystal. Extension of this nanometer-scale nuclear magnetic resonance (nanoNMR) to two-dimensional nanometer-scale magnetic resonance imaging (2D nanoMRI) is also presented.

The nitrogen delta-doping technique is combined with shallow 12C ion implantation through lithographically-patterned apertures to demonstrate three-dimensional (3D) localization of single NV centers at nanometer scale. The demonstrated long spin coherence times of 3D-localized NV centers pave a way towards quantum applications by maximizing their interactions to the diamond-based nanostructures.