High ensemble concentration of photo-stable NV centers in Type Ib nanodiamonds by thermal assisted migration of native vacancies

Abstract

Ion implantation and subsequent vacuum annealing is a conventional technique to fabricate nitrogen vacancy (NV) centers in nanodiamonds (NDs) for different applications where high emission collection is required. In this work, we have explored as-grown lattice vacancies for creation of NV centers in NDs by making them migrate using high temperature isothermal heat treatment. The concentration of NV centers is maximized at optimized fabrication parameters of heat treatment (1000 °C with residual time of 1 h in vacuum environment) and subsequent air oxidation (575 °C, 2 h). The results show that optimized NV fabrication parameters lead to high photo-stability of NDs both at ensemble as well as individual ND particle level. The obtained NV− concentration of ~6.7 ppm is comparable to that of the sample irradiated by He2+ ions having beam energy of 50 keV and fluence of 1013 ions/cm2 (~12.5 ppm), with higher ensemble photo-stability than the later. Our results, which demonstrate that high concentration NV centers with high photo-stability is achievable by low cost processing without employing the ion implantation, thus can contribute to the fields of optical bio-imaging and ensemble magnetometry which require bright emission from NV centers.