Number Of NV Research Articles

The concentration estimation for ensemble of NV– color centers with spin coherent manipulation

The concentration and distribution of negatively charged nitrogen-vacancy color centers (NV−) directly affect the sensitivity and resolution of quantum sensing. In this paper, a simple method is proposed to estimate the concentration of the ensemble of NV− centers with spin coherent manipulation. The stray fluorescence is eliminated by separating the fluorescence near the NV− zero-phonon line. By introducing a single NV− fluorescence quantitative model, the number of NV− centers in the diamond under test can be obtained. The average concentration of the ensemble of NV− centers in the sample can be obtained by combining the detection volume. Compared with the results measured by electron spin resonance, the concentration of NV− centers measured by our method can be verified, and the maximum error between the two methods is less than 4.3%. The results show that the method provides an effective reference for accurately characterizing the concentration distribution characteristics of the NV− ensemble.

Advances in Stabilization and Enrichment of Shallow Nitrogen-Vacancy Centers in Diamond for Biosensing and Spin-Polarization Transfer.

Negatively charged nitrogen-vacancy (NV-) centers in diamond have unique magneto-optical properties, such as high fluorescence, single-photon generation, millisecond-long coherence times, and the ability to initialize and read the spin state using purely optical means. This makes NV- centers a powerful sensing tool for a range of applications, including magnetometry, electrometry, and thermometry. Biocompatible NV-rich nanodiamonds find application in cellular microscopy, nanoscopy, and in vivo imaging. NV- centers can also detect electron spins, paramagnetic agents, and nuclear spins. Techniques have been developed to hyperpolarize 14N, 15N, and 13C nuclear spins, which could open up new perspectives in NMR and MRI. However, defects on the diamond surface, such as hydrogen, vacancies, and trapping states, can reduce the stability of NV- in favor of the neutral form (NV0), which lacks the same properties. Laser irradiation can also lead to charge-state switching and a reduction in the number of NV- centers. Efforts have been made to improve stability through diamond substrate doping, proper annealing and surface termination, laser irradiation, and electric or electrochemical tuning of the surface potential. This article discusses advances in the stabilization and enrichment of shallow NV- ensembles, describing strategies for improving the quality of diamond devices for sensing and spin-polarization transfer applications. Selected applications in the field of biosensing are discussed in more depth.

Multi-focal laser fabrication of nitrogen vacancy centres in a bulk diamond

We demonstrate the multi-focal fabrication of single N V − centres at different depths in a bulk diamond. After performing an annealing process, the optically detected magnetic resonance (ODMR) signal is measured to confirm the generation of N V − centres. These emitters are photo-stable and are imaged by using three different excitations wavelengths at different depths close to the bulk diamond surface. Using two-photon microscopy, the N V − centres are imaged with a resolution down to 0.36 µm to study the effect of the exposure time of the multi-focal laser writing on the spatial resolution of each fabrication. The Hanbury Brown and Twiss (HBT) test is performed with two-photon excitation to study the number of N V − centres at the location of each multi-focal fabrication. We demonstrate the formation of single N V − centres placed between 100 nm and 3 µm below the diamond surface. The ability to control the placement of single N V − centres with depth is of paramount importance for applications in quantum information, single spin magnetometry, and optical data storage.

Quantitative analysis of spectral characteristics and concentration of ensembles of NV− centers in diamond

On account of their outstanding photo-luminescence properties, NV− (nitrogen-vacancy) centers in diamond make possible the high-sensitivity detection of physical quantities. The concentration of NV− centers is one of the main factors that affect the sensitivity in detecting macroscopic physical quantities. This paper studied and analyzed the relationship between the dose of electron irradiation and the concentration of NV− centers. We found that after electron irradiation into diamond, luminescence centers of 524.7nm, 541.1nm, 578nm and 648.1nm were formed, which is necessary for producing NV− centers. After annealing at high temperature (≥800°C) and in vacuum (≥10−7Pa) on diamond, NV− centers were formed when vacancies were bound by nitrogen atoms. We also obtained the rules of NV− concentration as a function of electron irradiation, which followed Boltzmann distribution. In addition, the number of NV− produced by electron injection was limited by 16ppm for diamond with a nitrogen content of 100ppm regardless of the increment of vacancies concentration. This study is the basis of quantitative preparation of NV−centers, and further lays a foundation for the application of NV− centers to the precise measurement of macroscopic physical qualities.