Abstract The diamond nitrogen-vacancy center with a negative charge (NV−) exhibits exceptional optical properties and enables highly sensitive detection of multiple physical quantities. The development of a simple and efficient method for fabricating NV− centers in diamonds holds significant importance in promoting their widespread application. The fabrication method of NV− centers is explored in this work, utilizing high-energy photons emitted by argon ions to induce vacancies in type Ia diamond substrates. The processed samples are optical characterized, and the characteristic peak and zero phonon line corresponding to the NV− center can be observed in Raman and photoluminescence spectra respectively. The concentration of NV− centers in samples could reach up to 153.9 ppb, estimated by integrating the fluorescence intensity of the photoemission spectrum. The samples exhibit the spin characterization of NV− centers, which achieve a maximum contrast of 1.5% in the optical detection magnetic resonance (ODMR) spectra.
Abstract The diamond nitrogen-vacancy center with a negative charge (NV−) exhibits exceptional optical properties and enables highly sensitive detection of multiple physical quantities. The development of a simple and efficient method for fabricating NV− centers in diamonds holds significant importance in promoting their widespread application. The fabrication method of NV− centers is explored in this work, utilizing high-energy photons emitted by argon ions to induce vacancies in type Ia diamond substrates. The processed samples are optical characterized, and the characteristic peak and zero phonon line corresponding to the NV− center can be observed in Raman and photoluminescence spectra respectively. The concentration of NV− centers in samples could reach up to 153.9 ppb, estimated by integrating the fluorescence intensity of the photoemission spectrum. The samples exhibit the spin characterization of NV− centers, which achieve a maximum contrast of 1.5% in the optical detection magnetic resonance (ODMR) spectra.
Precise control over the spatial distribution and charge state of nitrogen-vacancy (NV) centers in diamond is a key requirement for further advancing this platform in quantum sensing and photonic applications. Here, we investigate nitrogen ion implantation as a scalable method to engineer NV centers in bulk single-crystalline (SC) and a 5 μ m -thick polycrystalline (PC) diamond membrane. Nitrogen-doped regions (1–80 ppm) were fabricated using a 0.7 MeV ion beam and high-temperature annealing, with NV center formation verified by confocal fluorescence imaging and spectral analysis. In SC bulk diamond, we estimate the NV concentration from spectral analysis and model the fluorescence response as a function of implantation dose, capturing both the initial increase at low concentrations and a saturation behavior at higher doses due to quenching mechanisms. In contrast, PC diamond membranes show a weaker dependence at low implantation fluences, consistent with pre-existing nitrogen impurities, thus making a statistical model significantly more complex. The activation yield is found to be of order of 1%, which is lower than in N-rich diamond samples, as implanted N is predominantly interstitial. Photoluminescence spectroscopy indicates that NV 0 is the dominant charge state in both materials, with a laser-power-dependent redistribution between neutral and negative charge states. Optically detected magnetic resonance (ODMR) measurements in SC bulk diamond resolve the hyperfine structure and allow extraction of the dephasing time ( T 2 ∗ ), while in PC diamond membranes, where NV centers tend do form near the grain boundaries, the ODMR signals are observed but spectral resolution is currently limited by impurities, grain-dependent NV orientations, and photoluminescence background.
Quantum information applications place stringent demands on the development of platforms that can host them. Color centers in diamond have been identified as important media for quantum information processing. Accordingly, the photoluminescence properties of nitrogen-vacancy (N-V) centers in diamond created by implantation and annealing are studied at cryogenic temperatures (below 10 K). We examine high pressure high temperature and chemical vapor deposition synthetic diamonds with varying nitrogen concentration and present an accurate method to estimate the concentration of the (N-V) centers created by ion implantation. The ion irradiation route produced up to 6 ppm of optically active (N-V) centers, while nitrogen implantation yielded up to 3 ppm of optically active (N-V) with 8% conversion efficiency. However, a broadening of the (N-V)− zero phonon line was observed in all samples.
Nitrogen-vacancy (NV) centers in single-crystal CVD diamond are promising candidates for quantum sensing due to their remarkable optical and spin properties [1]. These defects exhibit stable photoluminescence (PL), long spin coherence times, and high sensitivity to external fields [2]. In this study, we present a room-temperature PL characterization of NV centers excited with a 532 nm laser. The setup was optimized for high signal-to-noise ratio and spectral resolution. Key parameters analyzed include emission intensity, zero-phonon line (ZPL) at ~637 nm, phonon sidebands, and the charge state distribution between NV⁰ and NV⁻. The NV⁻ state, crucial for spin-based sensing, is evaluated to understand its stability under different nitrogen doping conditions [3]. The relative intensities of NV⁰ and NV⁻ provide insights into nitrogen incorporation and vacancy formation. These results contribute to optimizing synthesis conditions for enhanced NV⁻ concentration, supporting the advancement of diamond-based quantum sensing technologies.
Nitrogen-vacancy (NV) color centers in diamond are excellent quantum sensors possessing high sensitivity and nano-scale spatial resolution. Their integration in photonic structures is often desired, since it leads to an increased photon emission and also allows the realization of solid-state quantum technology architectures. Here, we report the fabrication of diamond nano-pillars with diameters up to 1000 nm by electron beam lithography and inductively coupled plasma reactive ion etching in nitrogen-rich diamonds (type Ib) with [100] and [111] crystal orientations. The NV centers were created by keV-He ion bombardment and subsequent annealing, and we estimate an average number of NVs per pillar to be 4300 ± 300 and 520 ± 120 for the [100] and [111] samples, respectively. Lifetime measurements of the NVs’ excited state showed two time constants with average values of τ1 ≈ 2 ns and τ2 ≈ 8 ns, which are shorter as compared to a single color center in a bulk crystal (τ ≈ 10 ns). This is probably due to a coupling between the NVs as well as due to interaction with bombardment-induced defects and substitutional nitrogen (P1 centers). Optically detected magnetic resonance measurements revealed a contrast of about 5% and average coherence and relaxation times of T2 [100] = 420 ± 40 ns, T2 [111] = 560 ± 50 ns, and T1 [100] = 162 ± 11 μs, T1 [111] = 174 ± 24 μs. These pillars could find an application for scanning probe magnetic field imaging.
Raman and ODMR Spectroscopy of NV Centers in Nanolayers and Nanopillars of ⟨111⟩ Diamond after Etching with a Focused Beam of Ga Ions
The spectral characteristics of the optically detected magnetic resonance of negatively charged nitrogen–vacancy (NV − ) centers in synthetic diamonds and nanopillars on their surface formed by a focused Ga + ion beam, when the lower spin sublevels are populated with microwave radiation, are studied. In the course of studies for emerging spin resonances at different values of the external magnetic field, both a significant decrease in the gyromagnetic ratio and a significant drop in the photoluminescence contrast are revealed for the directions of the NV − centers inclined to the axis of the nanopillars due to residual defects from ion etching recorded on Raman spectra in the form of peaks from amorphous carbon and graphite and the stresses they create.
Among promising color centers for single-photon sources in diamond, the negatively charged silicon-vacancy (SiV − ) has 70% of its emission to the zero-phonon line (ZPL), in contrast to the negatively charged nitrogen vacancy (NV − ), which has a broad spectrum. Fabricating single centers of useful defect complexes with high yield and excellent grown-in defect properties by ion implantation has proven to be challenging. We have fabricated bright single SiV − centers by 60-keV focused ion beam implantation and subsequent annealing at 1000 °C with high positioning accuracy and a high yield of 15%.