Creation of NV Centers in Diamond under 155 MeV Electron Irradiation
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-11-20 |
| Journal | Advanced Physics Research |
| Authors | Elena Losero, V. Goblot, Yuchun Zhu, Hossein Babashah, Victor Boureau |
| Institutions | Deutsches Elektronen-Synchrotron DESY, Ăcole Polytechnique FĂ©dĂ©rale de Lausanne |
| Citations | 4 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Yield NV Center Creation via 155 MeV Electron Irradiation
Section titled âTechnical Documentation & Analysis: High-Yield NV Center Creation via 155 MeV Electron IrradiationâSource Paper: Creation of NV Centers in Diamond under 155 MeV Electron Irradiation (Losero et al., Adv. Physics Res. 2024)
Executive Summary
Section titled âExecutive SummaryâThis research validates an advanced methodology for creating high-density nitrogen-vacancy (NV$^-$) ensembles in diamond using extremely high energy (EHE) electron irradiation, a critical step for scaling quantum sensing applications.
- High Yield NV$^-$ Creation: 155 MeV electron irradiation demonstrated a $\sim$60-fold higher NV$^-$ concentration yield compared to conventional 200 keV irradiation for the same substrate and fluence.
- Enhanced Sensitivity: The resulting NV$^-$ ensembles achieved concentrations up to 0.6 ppm in HPHT diamond, translating to a $\sim$45x improvement in projected optically detected magnetic resonance (ODMR) sensitivity.
- Near-Ideal Charge Conversion: The process maintained a high charge state conversion efficiency ($\xi$) of >90% in the maximally irradiated region, ensuring the majority of defects are in the desired NV$^-$ state.
- Macroscopic Volume Processing: Simulations and experiments confirm uniform vacancy generation across the entire 0.3 mm sample thickness, with potential penetration depths exceeding 10 cm, enabling cost-effective batch irradiation of stacked substrates.
- Material Requirements: The study utilized commercial HPHT and CVD diamond, highlighting the need for high-quality, low-damage single crystal diamond (SCD) with precisely controlled nitrogen doping ([N]).
- 6CCVD Value Proposition: 6CCVD provides the necessary high-purity, custom-dimension SCD substrates and expert consultation required to replicate and scale this high-yield NV engineering technique.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research, focusing on the EHE irradiation regime and key performance metrics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Electron Irradiation Energy (EHE) | 155 | MeV | Primary experimental regime |
| Electron Irradiation Energy (LWE) | 200 | keV | Low energy comparison (TEM) |
| Maximum Fluence (EHE) | 1.5 $\cdot$ 1018 | e/cm2 | Target fluence for Sample 1 (HPHT) |
| Substrate Dimensions (HPHT) | 3 x 3 x 0.3 | mm3 | Sample 1 dimensions |
| Initial Nitrogen Concentration ([N]) | $\le$ 200 | ppm | HPHT substrate (Element6) |
| Achieved NV- Concentration | 0.6 | ppm | Maximum concentration (HPHT, 155 MeV) |
| NV- Yield Enhancement (155 MeV vs 200 keV) | $\sim$60 | times | For same substrate and fluence |
| Charge State Conversion Efficiency ($\xi$) | >90 | % | In maximally irradiated region |
| Projected Sensitivity Improvement | $\sim$45 | times | Compared to pristine HPHT sample |
| Thermal Annealing Temperature | 800 | °C | Standard post-irradiation treatment |
| Thermal Annealing Duration | 4 | hours | Standard post-irradiation treatment |
| Estimated Penetration Depth | >10 | cm | Potential for batch processing |
Key Methodologies
Section titled âKey MethodologiesâThe creation of high-density NV$^-$ ensembles relies on precise control over both the substrate material and the subsequent irradiation and annealing processes.
- Substrate Selection: Commercial diamond substrates were used: nitrogen-rich HPHT ([N] $\le$ 200 ppm) and low-nitrogen CVD ([N] $\le$ 1 ppm).
- High Energy Irradiation Setup: Electrons were accelerated to 155 MeV using a linear accelerator (ARES at DESY).
- Beam Characteristics: A Gaussian beam profile with a diameter of 2r $\sim$(500 $\pm$ 50) ”m was used to irradiate the sample along the y-axis.
- Fluence Control: The target fluence of 1.5 $\cdot$ 1018 e/cm2 was achieved by operating at high bunch charges (up to 120 pC/pulse) and a 10 Hz repetition rate over 96 hours.
- Low Energy Comparison: A standard 200 keV Transmission Electron Microscope (TEM) was used for comparison, applying fluences ranging from 1 $\cdot$ 1016 to 5 $\cdot$ 1020 e/cm2 in a 15 ”m diameter beam.
- Post-Irradiation Annealing: All irradiated samples underwent conventional low-pressure thermal annealing at 800 °C for 4 hours under P = 10-6 mbar to mobilize vacancies (V) and facilitate bonding with substitutional nitrogen (N) to form NV centers.
- Characterization: NV$^-$ concentration and charge state conversion efficiency ($\xi$) were quantified using Photoluminescence (PL) spectroscopy and ODMR measurements.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD specializes in providing the high-quality, customized MPCVD diamond substrates essential for advanced quantum sensing research, such as the high-yield NV creation demonstrated in this paper. Our capabilities directly address the material requirements for replicating and scaling this EHE irradiation technique.
Applicable Materials
Section titled âApplicable MaterialsâTo successfully replicate or extend this research, high-purity diamond with precise nitrogen control is mandatory.
- Optical Grade SCD: Required for replicating the low-nitrogen CVD experiments ([N] $\le$ 1 ppm) or for applications requiring long coherence times (T2). 6CCVD provides SCD with Ra < 1 nm polishing.
- High-Purity SCD (Controlled Doping): Ideal for replicating the high-yield ensemble sensing results achieved with the HPHT substrate ([N] $\le$ 200 ppm). We offer SCD with tunable nitrogen incorporation during MPCVD growth to optimize the critical [V]/[N] ratio.
- Polycrystalline Diamond (PCD): For large-area, cost-sensitive applications, 6CCVD offers PCD wafers up to 125mm in diameter, suitable for macroscopic ensemble sensing where the high penetration depth of 155 MeV electrons is leveraged.
Customization Potential
Section titled âCustomization PotentialâThe paper highlights the potential for batch processing of substrates stacked up to >10 cm. 6CCVDâs custom manufacturing capabilities are perfectly suited to supply the necessary volume and precision.
| Research Requirement | 6CCVD Customization Service | Specification Range |
|---|---|---|
| Macroscopic Volume Processing | Custom SCD and PCD plates/wafers. | Wafers up to 125mm (PCD). Substrates up to 10 mm thick. |
| Precise Thickness Control | SCD and PCD thickness control. | 0.1 ”m to 500 ”m (SCD/PCD). |
| High-Quality Optical Readout | Ultra-low roughness polishing. | Ra < 1 nm (SCD); Ra < 5 nm (Inch-size PCD). |
| Integrated Sensor Fabrication | Custom metalization services. | Deposition of Au, Pt, Pd, Ti, W, Cu for microwave antennas or electrodes post-annealing. |
| Global Supply Chain | Global shipping options. | DDU (default) and DDP available worldwide. |
Engineering Support
Section titled âEngineering SupportâThe optimization of NV creation relies heavily on complex material science, including managing cascade effects, vacancy recombination, and the precise [V]/[N] ratio.
- Material Selection Consultation: 6CCVDâs in-house PhD team provides expert assistance in selecting the optimal SCD or PCD grade and nitrogen doping level required to maximize NV$^-$ yield and maintain long spin relaxation times (T1) for similar Quantum Sensing and Magnetometry projects.
- Process Optimization: We offer consultation on post-growth processing parameters, including material stability under high-energy irradiation and thermal annealing recipes (800 °C, low pressure) to ensure high charge state conversion efficiency ($\xi$).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Singleâcrystal diamond substrates presenting a high concentration of negatively charged nitrogenâvacancy centers (NV â ) are on high demand for the development of optically pumped solidâstate sensors such as magnetometers, thermometers, or electrometers. While nitrogen impurities can be easily incorporated during crystal growth, the creation of vacancies requires further treatment. Electron irradiation and annealing is often chosen in this context, offering advantages with respect to irradiation by heavier particles that negatively affect the crystal lattice structure and consequently the NV â optical and spin properties. A thorough investigation of electron irradiation possibilities is needed to optimize the process and improve the sensitivity of NVâbased sensors. In this work, the effect of electron irradiation is examined in a previously unexplored regime: extremely high energy electrons, at 155 MeV. A simulation model is developed to estimate the concentration of created vacancies and an increase of NV â concentration by more than three orders of magnitude following irradiation of a nitrogenârich HPHT diamond over a very large sample volume is experimentally demonstrated, which translates into an important gain in sensitivity. Moreover, the impact of electron irradiation in this peculiar regime on other figures of merits relevant for NV sensing is discussed, including charge state conversion efficiency and spin relaxation time. Finally, the effect of extremely high energy irradiation is compared with the more conventional low energy irradiation process, employing 200 keV electrons from a transmission electron microscope, for different substrates and irradiation fluences, evidencing 60âfold higher yield of vacancy creation per electron at 155 MeV.