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窒素不純物がダイヤモンド中のNVセンターの量子収率を減少させる効果についての研究, 14th International Conference on New Diamond and Nano Carbons 2020/2021

The nitrogen-vacancy (NV) center in diamond is a promising quantum system for magnetometry applications exhibiting optical readout of minute energy shifts in its spin sub-levels. Key material requirements for NV ensembles are a high NV- concentration, a long spin coherence time and a stable charge state. However, these are interdependent and can be difficult to optimize during diamond growth and subsequent NV creation. In this work, we systematically investigate the NV center formation and properties in bulk chemical vapor deposition (CVD) diamond. The nitrogen flow during growth is varied by over 4 orders of magnitude, resulting in a broad range of single substitutional nitrogen concentrations of 0.2-20~parts per million. For a fixed nitrogen concentration, we optimize electron-irradiation fluences with two different accelerated electron energies, and we study defect formation via optical characterizations. We discuss a general approach to determine the optimal irradiation conditions, for which an enhanced NV concentration and an optimum of NV charge states can both be satisfied. We achieve spin-spin coherence times T2 ranging from 45.5 to 549 μs for CVD diamonds containing 168 to 1~parts per billion NV- centers, respectively. This study shows a pathway to engineer properties of NV-doped CVD diamonds for improved sensitivity.

In-plain pi(n-)n diodes were fabricated on n-type epitaxial 4H-SiC layer grown on a n-type 4H-SiC substrate. As a result of confocal photoluminescence measurements, two types of single photon sources were observed in n-type region of 4H-SiC pin diodes, International Union of Materials Research Societies, The 15th International Conference on Advanced Materials (IUMRS-ICAM2017)

Although traditional optical fibers are not sensitive to magnetic fields, many applications would benefit from fiber-based magnetometry devices. In this study, a magnetically sensitive optical fiber was demonstrated using doping nanodiamonds containing nitrogen vacancy centers into tellurite glass fibers. The fabrication process provides a robust and isolated sensing platform as the magnetic sensors are fixed in the tellurite glass matrix. Using optically detected magnetic resonance from the doped nanodiamonds, detection of local magnetic fields via side excitation and longitudinal collection were demonstrated. This is an important step towards intrinsically magneto-sensitive fiber devices with future applications in medical magneto-endoscopy and remote mineral exploration sensing.