Long dephasing time of NV center spins in diamond layers formed by hot ion implantation and high pressure high temperature annealing

Thin nitrogen doped layers with ~1 ppm NV center ensembles were created by the hydrogen implantation of type Ib or hot nitrogen implantation in the high purity type IIa and IIb high pressure high temperature-grown (HPHT) diamond and followed HPHT treatment up to 1500 °C at 7 GPa. The dephasing time T2* = 0.4–0.9 μs was obtained even for the implanted nitrogen content of ~100 ppm. The data evidence the absence of other spin active defects besides the implanted nitrogen atoms in neutral states, determined this decoherence.