Atomic-size spin defects in solids are unique quantum systems. Most applications require nanometre positioning accuracy, which is typically achieved by low-energy ion implantation. A drawback of this technique is the significant residual lattice damage, which degrades the performance of spins in quantum applications. Here we show that the charge state of implantation-induced defects drastically influences the formation of lattice defects during thermal annealing. Charging of vacancies at, for example, nitrogen implantation sites suppresses the formation of vacancy complexes, resulting in tenfold-improved spin coherence times and twofold-improved formation yield of nitrogen-vacancy centres in diamond. This is achieved by confining implantation defects into the space-charge layer of free carriers generated by a boron-doped diamond structure. By combining these results with numerical calculations, we arrive at a quantitative understanding of the formation and dynamics of the implanted spin defects. These results could improve engineering of quantum devices using solid-state systems.

Quantum information technologies require networks of interacting defect bits. Colour centres, especially the nitrogen vacancy (NV − ) centre in diamond, represent one promising avenue, toward the realisation of such devices. The most successful technique for creating NV − in diamond is ion implantation followed by annealing. Privious experiments have shown that shallow nitrogen implantation (<10keV) results in NV − centres with a yield of 0.01 − 0.1%. We investigate the influence of channeling effects during shallow implantation and statistical diffusion of vacancies using molecular dynamics (MD) and Monte Carlo (MC) simulation techniques. Energy barriers for the diffusion process were calculated using density functional theory (DFT). Our simulations show that 25% of the implanted nitrogens form an NV centre, which is in good agreement with our experimental findings.