  We demonstrate nanometer-precision depth control of nitrogen-vacancy (NV)
center creation near the surface of synthetic diamond using an in situ nitrogen
delta-doping technique during plasma-enhanced chemical vapor deposition.
Despite their proximity to the surface, doped NV centers with depths (d)
ranging from 5 - 100 nm display long spin coherence times, T2 > 100 \mus at d =
5 nm and T2 > 600 \mus at d \geq 50 nm. The consistently long spin coherence
observed in such shallow NV centers enables applications such as atomic-scale
external spin sensing and hybrid quantum architectures.
