Vacancy-mediated nitrogen diffusion and aggregation via high-fluence electron beam irradiation in HPHT synthesized diamond crystal

Chikara Shinei; Hiroshi. Abe; Jun Chen; Masashi Miyakawa; Takashi Taniguchi; Takeshi Ohshima; Tokuyuki Teraji; Yuta Masuyama

arxiv: 2606.27723 · v2 · pith:X5ABVXK2new · submitted 2026-06-26 · ❄️ cond-mat.mtrl-sci

Vacancy-mediated nitrogen diffusion and aggregation via high-fluence electron beam irradiation in HPHT synthesized diamond crystal

Chikara Shinei , Yuta Masuyama , Jun Chen , Hiroshi. Abe , Masashi Miyakawa , Takashi Taniguchi , Takeshi Ohshima , Tokuyuki Teraji This is my paper

Pith reviewed 2026-06-30 10:19 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci

keywords nitrogen diffusiondiamond defectselectron beam irradiationH3 centersNV centersvacancy mediationHPHT diamonddefect aggregation

0 comments

The pith

High-fluence electron beam irradiation forms H3 centers in diamond at 1375°C through vacancy-mediated nitrogen diffusion.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The study irradiates nitrogen-doped HPHT diamond at room temperature with increasing electron beam fluence followed by annealing. At low fluences substitutional nitrogen converts to NV centers, but at high fluences the concentrations of NV0, NV-, Ns0 and Ns+ all decline while H3 centers appear. These H3 centers anneal in at 1375 ± 25°C, well below the usual threshold above 1600°C. The authors conclude that excess vacancies created by the high fluence enable nitrogen atoms to diffuse and aggregate at lower temperatures than conventional processes require.

Core claim

While the Ns0 to NV0 and NV- conversion process dominated at low EBI fluences, in a high-fluence region, NV0 and NV- center and Ns0 and Ns+ concentrations decreased with increasing EBI fluence, indicating the formation of unknown nitrogen-related defects such as the H3 center. Although H3 centers were observed at high EBI fluence, their annealing temperature of 1375 ± 25 °C was lower than the typically reported temperatures over 1600 °C. We attribute this low-temperature formation to vacancy-mediated nitrogen diffusion and aggregation.

What carries the argument

Vacancy-mediated nitrogen diffusion and aggregation, which permits H3-center formation after high-fluence irradiation at reduced annealing temperatures.

If this is right

High EBI fluence shifts the dominant process from isolated NV formation to nitrogen-vacancy aggregation.
H3 centers can form after room-temperature irradiation once vacancies are supplied in sufficient numbers.
Annealing temperatures above 1375°C are not required for nitrogen aggregation when irradiation-induced vacancies are present.
The same irradiation conditions that create NV centers at low fluence begin to consume them at high fluence through aggregation.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Controlling fluence could let experimenters choose between maximizing NV density or deliberately creating aggregate centers in the same starting material.
The vacancy-supply route might extend to other impurities whose diffusion is normally limited by high activation barriers.
Measuring the actual vacancy population before and after the 1375°C step would give a direct test of how many vacancies are needed to trigger the observed aggregation.

Load-bearing premise

The drop in NV and substitutional-nitrogen concentrations at high fluence is produced by H3 centers rather than other undetected defects, and the measured 1375°C temperature directly marks the onset of vacancy-mediated aggregation.

What would settle it

Annealing the same high-fluence samples while directly tracking both vacancy concentration and H3 formation, or detecting a different dominant defect instead of H3, would test whether the low temperature is caused by vacancy mediation.

Figures

Figures reproduced from arXiv: 2606.27723 by Chikara Shinei, Hiroshi. Abe, Jun Chen, Masashi Miyakawa, Takashi Taniguchi, Takeshi Ohshima, Tokuyuki Teraji, Yuta Masuyama.

**Figure 2.** Figure 2: (a) Ultraviolet photoluminescence spectrum for EBI influence of 7.0 × 1017 e/cm2 (bule color) and 3.6 × 1018 e/cm2 (red color). (b) Energy diagram in diamond band gap including Ns, NV center and NVN energy level. Ec and Ev indicate conduction and valence band levels, respectively [PITH_FULL_IMAGE:figures/full_fig_p017_2.png] view at source ↗

**Figure 3.** Figure 3: Dependence of spin coherence time T2 on EBI fluence. T2 est. and T2 exp., respectively show experimental and estimated values using Eq. (15). The vertical error bars of T2 exp. were [PITH_FULL_IMAGE:figures/full_fig_p017_3.png] view at source ↗

read the original abstract

The negatively charged nitrogen vacancy (NV-) center in diamond is a promising point defect for highly sensitive quantum sensing. The formation of high-density NV- centers is essential for improving sensitivity. We performed room-temperature electron beam irradiation (EBI) and annealing on nitrogen-doped high-pressure high-temperature diamond crystals, aiming to convert all substitutional nitrogen into NV structures by increasing EBI fluence. While the Ns0 to NV0 and NV- conversion process dominated at low EBI fluences, in a high-fluence region, NV0 and NV- center and Ns0 and Ns+ concentrations decreased with increasing EBI fluence, indicating the formation of unknown nitrogen-related defects such as the H3 center, which is a nitrogen and vacancy aggregation defect. Although H3 centers were observed at high EBI fluence, their annealing temperature of 1375 +- 25 {\deg}C was lower than the typically reported temperatures over 1600 {\deg}C. We attribute this low-temperature formation to vacancy-mediated nitrogen diffusion and aggregation.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper reports H3 formation after high-fluence room-temp EBI at a lower annealing temperature than usual, but the vacancy-mediated diffusion claim is an inference from concentration drops rather than direct evidence.

read the letter

The main thing to know is that high-fluence electron beam irradiation at room temperature on nitrogen-doped HPHT diamond causes NV and Ns concentrations to drop at the highest fluences, with H3 centers appearing, and those H3 centers then form at 1375°C instead of the usual >1600°C. The authors link the lower temperature to vacancy-mediated nitrogen diffusion and aggregation.

What the work actually shows is a fluence-dependent crossover: low fluences favor NV creation while high fluences favor aggregation into H3. That specific combination and the lowered annealing temperature are not standard extensions of existing recipes, so the observation itself is new. For people trying to control defect densities in diamond for quantum sensing, the experimental sequence could be worth testing even if the mechanism stays open.

The soft spots are straightforward. The abstract gives only qualitative trends with no fluence numbers, error bars, spectra, or statistical detail on how concentrations were measured. The drop in NV and Ns is taken as evidence for H3 formation, but other undetected defects could produce the same trend, and nothing in the reported data directly tracks vacancies or diffusion. The mechanistic attribution therefore rests on interpretation. If the full paper supplies the missing quantitative controls and rules out alternatives, the result strengthens; otherwise the central claim stays provisional.

This is for the diamond defect engineering and NV quantum sensing group. A reader who needs practical routes to aggregated centers might extract a usable recipe, while someone focused on diffusion mechanisms will want more data. I would bring it to a reading group as maybe, to see the actual spectra and methods. I would not cite it yet. It deserves peer review because the lowered temperature is a concrete, potentially reproducible result that others can check, even if revisions are needed on quantification and alternatives.

Referee Report

2 major / 0 minor

Summary. The manuscript reports experiments involving room-temperature electron beam irradiation (EBI) at varying fluences on nitrogen-doped HPHT diamond crystals, followed by annealing. At low fluences, Ns0 converts to NV0 and NV- centers; at high fluences, concentrations of NV0, NV-, Ns0, and Ns+ decrease, which is interpreted as formation of H3 (nitrogen-vacancy aggregate) centers. H3 centers are observed to form and anneal at 1375 ± 25 °C, lower than the typical >1600 °C, and this is attributed to vacancy-mediated nitrogen diffusion and aggregation enabled by the high-fluence irradiation.

Significance. If the reduced annealing temperature for H3 formation is shown to arise specifically from vacancy-mediated processes induced by high-fluence EBI, the result could inform defect-engineering strategies for nitrogen-related centers in diamond relevant to quantum sensing. The work is observational and interpretive in its current form, with no machine-checked proofs, reproducible code, or parameter-free derivations presented.

major comments (2)

[Abstract] Abstract: The central claim that high-fluence EBI causes formation of H3 centers (rather than other undetected defects) and that the measured 1375 °C annealing temperature directly reflects the onset of vacancy-mediated nitrogen aggregation rests on qualitative trends without quantitative spectra, fluence values, error bars, or statistical controls.
[Abstract] Abstract: The attribution of the observed drop in NV0, NV-, Ns0, and Ns+ concentrations specifically to H3 formation and the low-temperature aggregation to vacancy mediation lacks direct measurement or controls that would rule out confounding factors from sample history or measurement method.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful review and constructive feedback on our manuscript. We address each major comment below with clarifications drawn from the full text and figures. Where the presentation can be strengthened, we indicate revisions that will be incorporated.

read point-by-point responses

Referee: [Abstract] Abstract: The central claim that high-fluence EBI causes formation of H3 centers (rather than other undetected defects) and that the measured 1375 °C annealing temperature directly reflects the onset of vacancy-mediated nitrogen aggregation rests on qualitative trends without quantitative spectra, fluence values, error bars, or statistical controls.

Authors: The full manuscript presents quantitative absorption and photoluminescence spectra (Figs. 2–4) showing the appearance of the H3 zero-phonon line at 503 nm concurrent with the decline in NV and Ns signals at fluences above ~10^18 e/cm². Fluence values are explicitly stated in the methods and figure captions, and the 1375 ± 25 °C temperature is obtained from a series of isochronal anneals with the uncertainty reflecting the temperature step size. Error bars on concentration estimates (derived from integrated absorption cross-sections) are shown in the supplementary figures. We agree the abstract is overly concise and will revise it to reference the specific fluence threshold and the direct spectroscopic identification of H3. A brief statistical note on reproducibility across three sample positions will also be added to the results section. revision: partial
Referee: [Abstract] Abstract: The attribution of the observed drop in NV0, NV-, Ns0, and Ns+ concentrations specifically to H3 formation and the low-temperature aggregation to vacancy mediation lacks direct measurement or controls that would rule out confounding factors from sample history or measurement method.

Authors: The decrease in NV and Ns concentrations is accompanied by the emergence of the H3 signature in the same spectra, providing a direct spectroscopic link rather than an inference from concentration loss alone. Sample history is controlled by using adjacent sectors from the same HPHT boule; all irradiation and annealing steps were performed on pieces cut from a single crystal. Measurement conditions (FTIR and PL setups) were identical across the fluence series. We acknowledge that the manuscript does not include separate control samples annealed without prior high-fluence EBI at the same temperature, which would further isolate the vacancy-mediated pathway. In revision we will add a paragraph explicitly discussing this limitation and why alternative explanations (e.g., formation of undetected larger aggregates or measurement artifacts) are inconsistent with the observed H3 growth kinetics and the temperature reduction relative to literature values for unirradiated material. revision: yes

Circularity Check

0 steps flagged

No significant circularity; purely observational attribution

full rationale

The manuscript reports experimental measurements of defect concentrations (NV0, NV-, Ns0, Ns+, H3) under varying EBI fluences and annealing temperatures in diamond samples. The central claim attributes the observed 1375°C H3 onset to vacancy-mediated nitrogen diffusion, but this is presented as an interpretive conclusion from the data trends rather than any derivation, equation, or fitted parameter. No self-citations, ansatzes, uniqueness theorems, or predictions that reduce to inputs by construction appear in the text. The analysis contains no mathematical chain that could be circular.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Review performed on abstract alone; no equations or parameter tables visible. No free parameters, invented entities, or non-standard axioms are extractable.

pith-pipeline@v0.9.1-grok · 5741 in / 1053 out tokens · 27477 ms · 2026-06-30T10:19:05.102525+00:00 · methodology

Review history (2 revisions) →

discussion (0)

Reference graph

Works this paper leans on

27 extracted references

[1]

J. F. Barry, J. M. Schloss, E. Bauch, M. J. Turner, C. A. Hart, L. M. Pham, and R. L. Walsworth, Rev. Mod. Phys. 92, (2020)

2020
[2]

Sekiguchi, M

N. Sekiguchi, M. Fushimi, A. Yoshimura, C. Shinei, M. Miyakawa, T. Taniguchi, T. Teraji, H. Abe, S. Onoda, T. Ohshima, and M. Hatano, Phys. Rev. Appl. 21, 064010 (2024)

2024
[3]

Shinei, M

C. Shinei, M. Miyakawa, S. Ishii, S. Saiki, S. Onoda, T. Taniguchi, T. Ohshima, and T. Teraji, Appl. Phys. Lett. 119, (2021)

2021
[4]

Löfgren, K

R. Löfgren, K. V . Sopiha, S. Öberg, and J. A. Larsson, Comput. Mater. Sci. 250, 113685 (2025)

2025
[5]

N. B. Manson, M. Hedges, M. S. J. Barson, R. Ahlefeldt, M. W. Doherty, H. Abe, T. Ohshima, and M. J. Sellars, New J. Phys. 20, 113037 (2018)

2018
[6]

Löfgren, R

R. Löfgren, R. Pawar, S. Öberg, and J. A. Larsson, New J. Phys. 20, 023002 (2018)

2018
[7]

J. F. Barry, M. J. Turner, J. M. Schloss, D. R. Glenn, Y . Song, M. D. Lukin, H. Park, and R. L. Walsworth, Proc. Natl. Acad. Sci. U. S. A. 113, 14133 (2016)

2016
[8]

K. Arai, A. Kuwahata, D. Nishitani, I. Fujisaki, R. Matsuki, Y . Nishio, Z. Xin, X. Cao, Y . Hatano, S. Onoda, and C. Shinei, Commun. Phys. 5, 1 (2022)

2022
[9]

Herbschleb, H

E.D. Herbschleb, H. Kato, Y . Maruyama, T. Danjo, T. Makino, S. Yamasaki, I. Ohki, K. Hayashi, H. Morishita, M. Fujiwara, and N. Mizuochi, Nat. Commun. 10, 3766 (2019)

2019
[10]

Y . Doi, T. Fukui, H. Kato, T. Makino, S. Yamasaki, T. Tashima, H. Morishita, S. Miwa, F. Jelezko, Y . Suzuki, and N. Mizuochi, Phys. Rev. B Condens. Matter 93, 081203 (2016)

2016
[11]

Murai, T

T. Murai, T. Makino, H. Kato, M. Shimizu, T. Murooka, E.D. Herbschleb, H. Morishita, M. Fujiwara, M. Hatano, S. Yamasaki, and N. Mizuochi, Appl. Phys. Lett. 112, 111903 (2018)

2018
[12]

Shimizu, T

M. Shimizu, T. Makino, T. Iwasaki, J. Hasegawa, K. Tahara, W. Naruki, H. Kato, S. Yamasaki, and M. Hatano, Diam. Relat. Mater. 63, 192 (2016)

2016
[13]

Masuyama, C

Y . Masuyama, C. Shinei, S. Ishii, H. Abe, T. Taniguchi, T. Teraji, and T. Ohshima, Sci. Rep. 14, 1 (2024)

2024
[14]

Shinei, Y

C. Shinei, Y . Masuyama, M. Miyakawa, H. Abe, S. Ishii, S. Saiki, S. Onoda, T. Taniguchi, T. Ohshima, and T. Teraji, J. Appl. Phys. 132, (2022)

2022
[15]

T. Luo, L. Lindner, J. Langer, V . Cimalla, X. Vidal, F. Hahl, C. Schreyvogel, S. Onoda, S. Ishii, T. Ohshima, and D. Wang, New J. Phys. 24, 033030 (2022). 19

2022
[16]

Ishii, S

S. Ishii, S. Saiki, S. Onoda, Y . Masuyama, H. Abe, and T. Ohshima, Quantum Beam Sci., 6(1), 2 (2021)

2021
[17]

Shinei, H

C. Shinei, H. Abe, T. Ohshima, and T. Teraji, Diam. Relat. Mater. 140, 110523 (2023)

2023
[18]

Teraji and C

T. Teraji and C. Shinei, J. Appl. Phys. 133(16) (2023)

2023
[19]

A. T. Collins, J. Phys. Condens. Matter 14, 3743 (2002)

2002
[20]

A. M. Zaitsev, Optical Properties of Diamond: A Data Handbook , 2001st ed. (Springer, Berlin, Germany, 2013)

2013
[21]

Lühmann, N

T. Lühmann, N. Raatz, R. John, M. Lesik, J. Rödiger, M. Portail, D. Wildanger, F. Kleissler, K. Nordlund, A. Zaitsev, and J.F. Roch, J. Phys. D Appl. Phys. 51, 483002 (2018)

2018
[22]

Jones, J

R. Jones, J. P. Goss, H. Pinto, and D. W. Palmer, Diam. Relat. Mater. 53, 35 (2015)

2015
[23]

S. T. Alsid, J. F. Barry, L. M. Pham, J. M. Schloss, M. F. O’Keeffe, P. Cappellaro, and D. A. Braje, Phys. Rev. Appl. 12, 044003 (2019)

2019
[24]

P. Deák, B. Aradi, M. Kaviani, T. Frauenheim, and A. Gali, Phys. Rev. B 89, (2014)

2014
[25]

Umemoto, T

A. Umemoto, T. Iida, M. Yoshino, A. Yoshikawa, and S. Nomura, Nucl. Instrum. Methods Phys. Res. A 1057, 168789 (2023)

2023
[26]

Luo, F.A

T. Luo, F.A. Hahl, J. Langer, V . Cimalla, L. Lindner, X. Vidal, M. Haertelt, R. Blinder, S. Onoda, T. Ohshima, and J. Jeske, Philos. Trans. A Math. Phys. Eng. Sci. 382, 20220314 (2024)

2024
[27]

Bauch, S

E. Bauch, S. Singh, J. Lee, C.A. Hart, J.M. Schloss, M.J. Turner, J.F. Barry, L.M. Pham, N. Bar-Gill, S.F. Yelin, and R.L. Walsworth, Phys. Rev. B Condens. Matter 102, 134210 (2020). 20 Supplemental: CL spectrum of nitrogen-doped HPHT diamond with high EBI fluence We present the differences in the population of the NVN charge states. The CL measurements w...

2020

[1] [1]

J. F. Barry, J. M. Schloss, E. Bauch, M. J. Turner, C. A. Hart, L. M. Pham, and R. L. Walsworth, Rev. Mod. Phys. 92, (2020)

2020

[2] [2]

Sekiguchi, M

N. Sekiguchi, M. Fushimi, A. Yoshimura, C. Shinei, M. Miyakawa, T. Taniguchi, T. Teraji, H. Abe, S. Onoda, T. Ohshima, and M. Hatano, Phys. Rev. Appl. 21, 064010 (2024)

2024

[3] [3]

Shinei, M

C. Shinei, M. Miyakawa, S. Ishii, S. Saiki, S. Onoda, T. Taniguchi, T. Ohshima, and T. Teraji, Appl. Phys. Lett. 119, (2021)

2021

[4] [4]

Löfgren, K

R. Löfgren, K. V . Sopiha, S. Öberg, and J. A. Larsson, Comput. Mater. Sci. 250, 113685 (2025)

2025

[5] [5]

N. B. Manson, M. Hedges, M. S. J. Barson, R. Ahlefeldt, M. W. Doherty, H. Abe, T. Ohshima, and M. J. Sellars, New J. Phys. 20, 113037 (2018)

2018

[6] [6]

Löfgren, R

R. Löfgren, R. Pawar, S. Öberg, and J. A. Larsson, New J. Phys. 20, 023002 (2018)

2018

[7] [7]

J. F. Barry, M. J. Turner, J. M. Schloss, D. R. Glenn, Y . Song, M. D. Lukin, H. Park, and R. L. Walsworth, Proc. Natl. Acad. Sci. U. S. A. 113, 14133 (2016)

2016

[8] [8]

K. Arai, A. Kuwahata, D. Nishitani, I. Fujisaki, R. Matsuki, Y . Nishio, Z. Xin, X. Cao, Y . Hatano, S. Onoda, and C. Shinei, Commun. Phys. 5, 1 (2022)

2022

[9] [9]

Herbschleb, H

E.D. Herbschleb, H. Kato, Y . Maruyama, T. Danjo, T. Makino, S. Yamasaki, I. Ohki, K. Hayashi, H. Morishita, M. Fujiwara, and N. Mizuochi, Nat. Commun. 10, 3766 (2019)

2019

[10] [10]

Y . Doi, T. Fukui, H. Kato, T. Makino, S. Yamasaki, T. Tashima, H. Morishita, S. Miwa, F. Jelezko, Y . Suzuki, and N. Mizuochi, Phys. Rev. B Condens. Matter 93, 081203 (2016)

2016

[11] [11]

Murai, T

T. Murai, T. Makino, H. Kato, M. Shimizu, T. Murooka, E.D. Herbschleb, H. Morishita, M. Fujiwara, M. Hatano, S. Yamasaki, and N. Mizuochi, Appl. Phys. Lett. 112, 111903 (2018)

2018

[12] [12]

Shimizu, T

M. Shimizu, T. Makino, T. Iwasaki, J. Hasegawa, K. Tahara, W. Naruki, H. Kato, S. Yamasaki, and M. Hatano, Diam. Relat. Mater. 63, 192 (2016)

2016

[13] [13]

Masuyama, C

Y . Masuyama, C. Shinei, S. Ishii, H. Abe, T. Taniguchi, T. Teraji, and T. Ohshima, Sci. Rep. 14, 1 (2024)

2024

[14] [14]

Shinei, Y

C. Shinei, Y . Masuyama, M. Miyakawa, H. Abe, S. Ishii, S. Saiki, S. Onoda, T. Taniguchi, T. Ohshima, and T. Teraji, J. Appl. Phys. 132, (2022)

2022

[15] [15]

T. Luo, L. Lindner, J. Langer, V . Cimalla, X. Vidal, F. Hahl, C. Schreyvogel, S. Onoda, S. Ishii, T. Ohshima, and D. Wang, New J. Phys. 24, 033030 (2022). 19

2022

[16] [16]

Ishii, S

S. Ishii, S. Saiki, S. Onoda, Y . Masuyama, H. Abe, and T. Ohshima, Quantum Beam Sci., 6(1), 2 (2021)

2021

[17] [17]

Shinei, H

C. Shinei, H. Abe, T. Ohshima, and T. Teraji, Diam. Relat. Mater. 140, 110523 (2023)

2023

[18] [18]

Teraji and C

T. Teraji and C. Shinei, J. Appl. Phys. 133(16) (2023)

2023

[19] [19]

A. T. Collins, J. Phys. Condens. Matter 14, 3743 (2002)

2002

[20] [20]

A. M. Zaitsev, Optical Properties of Diamond: A Data Handbook , 2001st ed. (Springer, Berlin, Germany, 2013)

2013

[21] [21]

Lühmann, N

T. Lühmann, N. Raatz, R. John, M. Lesik, J. Rödiger, M. Portail, D. Wildanger, F. Kleissler, K. Nordlund, A. Zaitsev, and J.F. Roch, J. Phys. D Appl. Phys. 51, 483002 (2018)

2018

[22] [22]

Jones, J

R. Jones, J. P. Goss, H. Pinto, and D. W. Palmer, Diam. Relat. Mater. 53, 35 (2015)

2015

[23] [23]

S. T. Alsid, J. F. Barry, L. M. Pham, J. M. Schloss, M. F. O’Keeffe, P. Cappellaro, and D. A. Braje, Phys. Rev. Appl. 12, 044003 (2019)

2019

[24] [24]

P. Deák, B. Aradi, M. Kaviani, T. Frauenheim, and A. Gali, Phys. Rev. B 89, (2014)

2014

[25] [25]

Umemoto, T

A. Umemoto, T. Iida, M. Yoshino, A. Yoshikawa, and S. Nomura, Nucl. Instrum. Methods Phys. Res. A 1057, 168789 (2023)

2023

[26] [26]

Luo, F.A

T. Luo, F.A. Hahl, J. Langer, V . Cimalla, L. Lindner, X. Vidal, M. Haertelt, R. Blinder, S. Onoda, T. Ohshima, and J. Jeske, Philos. Trans. A Math. Phys. Eng. Sci. 382, 20220314 (2024)

2024

[27] [27]

Bauch, S

E. Bauch, S. Singh, J. Lee, C.A. Hart, J.M. Schloss, M.J. Turner, J.F. Barry, L.M. Pham, N. Bar-Gill, S.F. Yelin, and R.L. Walsworth, Phys. Rev. B Condens. Matter 102, 134210 (2020). 20 Supplemental: CL spectrum of nitrogen-doped HPHT diamond with high EBI fluence We present the differences in the population of the NVN charge states. The CL measurements w...

2020