Nitrogen impurities help to stabilize the negatively-charged-state of ${\mathrm{NV}}^{-}$ in diamond, whereas magnetic fluctuations from nitrogen spins lead to decoherence of ${\mathrm{NV}}^{-}$ qubits. It is not known what donor concentration optimizes these conflicting requirements. Here we used 10-MeV ${}^{15}{\mathrm{N}}^{3+}$ ion implantation to create ${\mathrm{NV}}^{-}$ in ultrapure diamond. Optically detected magnetic resonance of single centers revealed a high creation yield of $40\pm 3\%$ from ${}^{15}{\mathrm{N}}^{3+}$ ions and an additional yield of $56\pm 3\%$ from ${}^{14}\mathrm{N}$ impurities. High-temperature anneal was used to reduce residual defects, and charge stable ${\mathrm{NV}}^{-}$, even in a dilute ${}^{14}\mathrm{N}$ impurity concentration of 0.06 ppb were created with long coherence times.

• Received 26 June 2014
• Revised 19 August 2014

DOI:https://doi.org/10.1103/PhysRevB.90.081117