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arXiv:2609.22937 · Physical Review Materials

Efficient creation of shallow NV$^-$ ensembles by high-angle ion implantation

Kento Sasaki, Hideyuki Watanabe, Tokuyuki Teraji, Takashi Taniguchi, Kenji Watanabe, Kensuke Kobayashi

quant-phcond-mat.mtrl-sciSubmitted Sep 19, 2026• Announced Sep 22, 2026• 0 citations
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Abstract

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 $^{15}$N ions at angles exceeding 60$^\circ$, 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.

Journal reference
Phys. Rev. Materials 10, 086202 (2026)
DOI
10.1103/d8vg-ntsg

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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 15^{15}15N ions at angles exceeding 60∘^\circ∘, 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.
Engineering shallow nitrogen-vacancy (NV) centers in diamond holds the key to unlocking new advances in nanoscale quantum sensing. We find that the creation of near-surface NVs through delta doping during diamond growth allows for tunable control over both NV depth confinement (with a twofold improvement relative to low-energy ion implantation) and NV density, ultimately resulting in highly-sensitive single defects and ensembles with coherence limited by NV-NV interactions. Additionally, we demonstrate the utility of our shallow delta-doped NVs by imaging magnetism in few-layer CrSBr, a two-dimensional magnet. We anticipate that the control afforded by near-surface delta doping will enable new developments in NV quantum sensing from nanoscale NMR to entanglement-enhanced metrology.
Abstract The negatively charged nitrogen-vacancy centre (so-called NV-centre) in diamond is one of the most promising systems for applications in quantum technologies because of the possibility to optically manipulate and read out the spin state of this defect, even at room temperature. Nevertheless, obtaining high NV densities (>500 ppb) close to the surface (5–20 nm) while maintaining good spin properties remain challenging. In this work we rely on a versatile ion implantation system allowing both implanting nitrogen using N 2 + and creating vacancies with He + ion bombardment at variable energies and fluence to create shallow NV ensembles. By optimizing the ion irradiation conditions as well as the surface preparation prior to treatment we successfully increase the amount of created colour centres while demonstrating narrow magnetic resonance linewidths.
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.
Scalable realizations of quantum network technologies utilizing the nitrogen vacancy center in diamond require creation of optically coherent NV centers in close proximity to a surface for coupling to optical structures. We create single NV centers by 15^{15}15N ion implantation and high-temperature vacuum annealing. Origin of the NV centers is established by optically detected magnetic resonance spectroscopy for nitrogen isotope identification. Near lifetime-limited optical linewidths (<<< 60 MHz) are observed for the majority of the normal-implant (7∘^\circ∘, ≈\approx≈ 100 nm deep) 15^{15}15NV centers. Long-term stability of the NV−^-− charge state and emission frequency is demonstrated. The effect of NV-surface interaction is investigated by varying the implantation angle for a fixed ion-energy, and thus lattice damage profile. In contrast to the normal implant condition, NVs from an oblique-implant (85∘^\circ∘, ≈\approx≈ 20 nm deep) exhibit substantially reduced optical coherence. Our results imply that the surface is a larger source of perturbation than implantation damage for shallow implanted NVs. This work supports the viability of ion implantation for formation of optically stable NV centers. However, careful surface preparation will be necessary for scalable defect engineering.
Dense and shallow ensembles of negatively charged nitrogen-vacancy center (NV−) with good optical and spin properties play a key role in the performance enhancement of diamond-based quantum sensors. Ion implantation enables precise control of NV− depth and density. However, at high ion fluence, this method is limited by low NV− creation yields and sample amorphization. Additionally, shallow NV− spin properties deteriorate due to surface proximity. In this paper, we study N2+ ion implantation at energies between 10 and 15 keV with fluences as high as 1×1015 ions/cm2 at temperatures of 20, 400, and 800°C to investigate the influence of implantation temperature on lattice damage, NV− creation yield, and NV− spin properties. Our results show that diamond maintains structural integrity at 800°C with fluences up to 1×1015 ions/cm2 without amorphization. Furthermore, high-temperature implantation improves NV− creation yields up to five times without compromising T2∗, T2, and T1, making it a promising approach to enhance the magnetic field sensitivity of NV− ensembles.
Enhanced magnetic field sensitivity of shallow NV−^-− ensembles via high-temperature implantation
Dense and shallow ensembles of negatively charged nitrogen-vacancy centers (NV−^-−) with good optical and spin properties play a key role in the performance enhancement of diamond-based quantum sensors. Ion implantation enables precise control of NV−^-− depth and density. However, at high ion fluence, this method is limited by low NV−^-− creation yields and sample amorphization. Additionally, shallow NV−^-− spin properties deteriorate due to surface proximity. In this paper, we study N2+_2^+2+​ ion implantation at energies between 10 and 15 keV with fluences as high as 1e15 ions/cm2 at temperatures of 20, 400 and 800°C to investigate the influence of implantation temperature on lattice damage, NV−^-− creation yield and NV−^-− spin properties. Our results show that diamond maintains structural integrity at 800°C with fluences up to 1e15 ions/cm2 without amorphization. Furthermore, high-temperature implantation improves NV−^-− creation yields up to five times without compromising T2∗^*∗, T2 and T1, making it a promising approach to enhance the magnetic field sensitivity of NV−^-− ensembles.