Title: Tailoring spin defects in diamond,
Abstract: Atomic-size spin defects in solids are unique quantum systems. Most
applications require nanometer positioning accuracy, which is typically
achieved by low energy ion implantation. So far, a drawback of this technique
is the significant residual implantation-induced damage to the lattice, which
strongly degrades the performance of spins in quantum applications. In this
letter we show that the charge state of implantation-induced defects
drastically influences the formation of lattice defects during thermal
annealing. We demonstrate that charging of vacancies localized at e.g.
individual nitrogen implantation sites suppresses the formation of vacancy
complexes, resulting in a tenfold-improved spin coherence time of single
nitrogen-vacancy (NV) centers in diamond. This has been achieved by confining
implantation defects into the space charge layer of free carriers generated by
a nanometer-thin boron-doped diamond structure. Besides, a twofold-improved
yield of formation of NV centers is observed. By combining these results with
numerical calculations, we arrive at a quantitative understanding of the
formation and dynamics of the implanted spin defects. The presented results
pave the way for improved engineering of diamond spin defect quantum devices
and other solid-state quantum systems.