  The controlled scaling of diamond defect center based quantum registers
relies on the ability to position NVs with high spatial resolution. Using ion
implantation, shallow (< 10 nm) NVs can be placed with accuracy below 20nm, but
generally show reduced spin properties compared to bulk NVs. We demonstrate the
augmentation of spin properties for shallow implanted NV centers using an
overgrowth technique. An increase of the coherence times up to an order of
magnitude (T_2 = 250 \mu s) was achieved. Dynamic decoupling of defects spins
achieves ms decoherence times. The study marks a further step towards achieving
strong coupling among defects positioned with nm precision.
