Nitrogen impurities help to stabilize the negatively-charged-state of NV$^-$ in diamond, whereas magnetic fluctuations from nitrogen spins lead to decoherence of NV$^-$ qubits. It is not known what donor concentration optimizes these conflicting requirements. Here we used 10-MeV $^{ 15}$N$^{ 3+}$ ion implantation to create NV$^-$ in ultrapure diamond. Optically detected magnetic resonance of single centers revealed a high creation yield of $40\pm3$% from $^{ 15}$N$^{ 3+}$ ions and an additional yield of $56\pm3$% from $^{ 14}$N impurities. High-temperature anneal was used to reduce residual defects, and charge stable NV$^-$, even in a dilute $^{ 14}$N impurity concentration of 0.06 ppb were created with long coherence times.
Categories: cond-mat.mes-hall cond-mat.mtrl-sci