Abstract Negatively charged nitrogen‐vacancy (NV − ) centers in diamond are appealing for quantum sensing applications due to their environmental sensitivity and long coherence times. Precise and scalable shallow color center creation is essential yet challenging for technological quantum applications. This is due to the involvement of several lengthy processes, such as ion implantation and thermal annealing of the samples. The latter process can be addressed by application of an alternative activation technique that bypasses the high‐temperature annealing. For this, nitrogen‐implanted regions on a diamond substrate are exposed to continuous‐wave 405 nm laser radiation. The illumination leads to local activation of NV − centers with photoluminescence yield saturation for regions activated with laser power at around 800 µW. For low implantation doses, single NV − centers are created with corresponding mean T 2 coherence time value around 71 µs. The NV − creation yield for the lower implantation doses match conventional creation methods, while higher doses show reduced yield values. However, the coherent properties are comparable to NV − centers within annealed samples. This shows that the activated NV − centers are well‐suited for advanced applications in quantum sensing and related technologies.
Abstract Negatively charged nitrogen‐vacancy (NV − ) centers in diamond are appealing for quantum sensing applications due to their environmental sensitivity and long coherence times. Precise and scalable shallow color center creation is essential yet challenging for technological quantum applications. This is due to the involvement of several lengthy processes, such as ion implantation and thermal annealing of the samples. The latter process can be addressed by application of an alternative activation technique that bypasses the high‐temperature annealing. For this, nitrogen‐implanted regions on a diamond substrate are exposed to continuous‐wave 405 nm laser radiation. The illumination leads to local activation of NV − centers with photoluminescence yield saturation for regions activated with laser power at around 800 µW. For low implantation doses, single NV − centers are created with corresponding mean T 2 coherence time value around 71 µs. The NV − creation yield for the lower implantation doses match conventional creation methods, while higher doses show reduced yield values. However, the coherent properties are comparable to NV − centers within annealed samples. This shows that the activated NV − centers are well‐suited for advanced applications in quantum sensing and related technologies.
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.
Efficient creation of shallow NV− ensembles by high-angle ion implantation
Negatively charged nitrogen-vacancy (NV−) centers located a few nanometers below the diamond surface are key quantum defects for nanoscale sensing of external spins. However, the creation of shallow NV− centers with high yield remains a materials challenge. Here, we demonstrate that high-angle ion implantation enhances the creation efficiency of shallow NV− centers. By implanting 15N ions at angles exceeding 60∘, we achieve high NV− yields approaching 10% with effective NV− depths below 10 nm. These yields are significantly higher than those typically reported for shallow NV− creation. The enhanced NV− yield is consistent with an increased vacancy-to-nitrogen ratio in the near-surface region, which is expected to promote NV formation during annealing. The created NV− ensembles show coherence properties comparable to those of single shallow NV− centers at similar depths, and allow detection of nuclear spins in van der Waals materials attached to the diamond surface. Our results establish geometric control of ion implantation as a simple and broadly applicable approach to engineer shallow vacancy-related quantum defects.
The negatively-charged nitrogen-vacancy (NV) center is the most studied optical center in diamond and is very important for applications in quantum information science. Many proposals for integrating NV centers in quantum and sensing applications rely on their tailored fabrication in ultra pure host material. In this study, we use ion implantation to controllably introduce nitrogen into high purity, low nitrogen chemical vapor deposition diamond samples. The properties of the resulting NV centers are studied as a function of implantation temperature, annealing temperature, and implantation fluence. We compare the implanted NV centers with native NV centers present deep in the bulk of the as-grown samples. The results for implanted NV centers are promising but indicate, at this stage, that the deep native NV centers possess overall superior optical properties. In particular, the implanted NV centers obtained after annealing at 2000 °C under a stabilizing pressure of 8 GPa showed an ensemble linewidth of 0.17 nm compared to 0.61 nm after annealing at 1000 °C. Over the same temperature range, the ensemble NV−/NV0 ratio increased by a factor of ∼5, although this was accompanied by an overall decrease in the NV count.
Abstract A novel creation procedure for the nitrogen-vacancy (NV) center in diamond is investigated. After shallow nitrogen implantation, a continuous-wave laser is used to induce NV formation, while simultaneously exciting fluorescence to enable live observation. Our investigations imply that a different mechanism than heat induced vacancy diffusion causes the formation of NV centers with this method and we suggest possible alternative pathways which could be responsible, based on the observed properties. Furthermore, we test the procedure for its capabilities for the controlled creation of single centers and show that the emergence of individual centers can be tracked, while achieving sub-micrometer spatial precision.
Split-vacancy color centers in diamonds are promising solid-state platforms for the implementation of photonic quantum technologies. These luminescent defects are commonly fabricated upon low-energy ion implantation and subsequent thermal annealing. Their technological uptake will require the availability of reliable methods for the controlled, large-scale production of localized individual photon emitters. This task is partially achieved by controlled ion implantation to introduce selected impurities in the host material and requires the development of challenging beam focusing or collimation procedures coupled with single-ion detection techniques. We report on the protocol for the direct optical activation of split-vacancy color centers in diamond via localized processing with a continuous-wave laser at mW optical powers. We demonstrate the activation of photoluminescent Mg- and Sn-related centers at both the ensemble and single-photon emitter levels in ion-implanted, high-purity diamond crystals without further thermal processing. The proposed lithographic method enables the activation of individual color centers at specific positions of a large-area sample by means of a relatively inexpensive equipment offering real-time, in situ monitoring of the process.
Creating dense and shallow nitrogen-vacancy (NV) ensembles with good spin properties is a prerequisite for developing diamond-based quantum sensors exhibiting better performance. Ion implantation is a key enabling tool for precisely controlling spatial localization and density of NV color centers in diamond. However, it suffers from a low creation yield, while higher ion fluences significantly damage the crystal lattice. In this work, we realize N2+ ion implantation in the 30–40 keV range at high temperatures. At 800 °C, NV's ensemble photoluminescence emission is three to four times higher than room temperature implanted films, while narrow electron spin resonance linewidths of 1.5 MHz, comparable to well-established implantation techniques, are obtained. In addition, we found that ion fluences above 2 × 1014 ions/cm2 can be used without graphitization of the diamond film, in contrast to room temperature implantation. This study opens promising perspectives in optimizing diamond films with implanted NV ensembles that could be integrated into quantum sensing devices.