On the creation of near-surface nitrogen-vacancy centre ensembles by implantation of type Ib diamond

Dense, near-surface (within 10 nm) ensembles of nitrogen-vacancy (NV) centres in diamond are rapidly moving into prominence as the workhorse of a variety of envisaged applications, ranging from the imaging of fast-fluctuating magnetic signals to the facilitation of nuclear hyperpolarisation. Unlike their bulk counterparts, near-surface ensembles suffer from charge stability issues and reduced NV formation efficiency due to the diamond surface's role as a vacancy sink during annealing and an electron sink afterwards. To this end, work is ongoing to determine the best methods for producing high-quality ensembles in this regime. Here we examine the prospects for creating such ensembles cost-effectively by implanting nitrogen-rich type Ib diamond with electron donors, aiming to exploit the high bulk nitrogen density to combat surface-induced band bending in the process. This approach has previously been successful at creating deeper ensembles, however we find that in the near-surface regime there are fewer benefits over nitrogen implantation into pure diamond substrates. Our results suggest that control over diamond surface termination during annealing is key to successfully creating high-yield near-surface NV ensembles generally, and implantation into type Ib diamond may be worth revisiting once that has been accomplished.