*4.2.1 Ion implantation method*

The NV centers can be generated by nitrogen ion implantation after the formation of diamond film. Nitrogen ion implantation provides an NV positioning accuracy that

#### **Figure 8.**

*Schematic illustration for the creation of NV defect in diamond by CVD.*

#### **Figure 9.**

*The creation of NV defect via nitrogen ion implantation. (a) Schematic illustration of implanted 15N+ leaving a trail of vacancies until settling into a final position. Vacancies mobilized by annealing can bind a nitrogen atom (implanted or native) to form an NV defect, and (b) a SRIM simulation using the parameters in sample shows the distribution of implanted nitrogen and created vacancies. Reproduced with permission from ref. [47]. Copyright 2019 American Physical Society.*

enables the integration with on-chip photonic devices [46]. Furthermore, this method can create a single NV center or a new NV defect coupling with the nearby NV defect. However, in the process of bombarding diamond with nitrogen ions, severe lattice damage in diamond is inevitable, resulting in damaging the ground state of NV defect and weakening the spin coherence time. Fortunately, it has been found that hightemperature annealing can recover part of the damaged lattice. In order to distinguish NV defects formed by implanted nitrogen atoms from the NV defects formed by
