Electron spin resonance of NV-=SUP=-(-)-=/SUP=--centers in synthetic fluorescent diamond microcrystals under conditions of optical spin polarization
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Оптика и спектроскопия |
| Authors | V. Yu. Osipov, Kirill Bogdanov, Arfaan Rampersaud, Kazuyuki Takai, Yasushi Ishiguro |
| Institutions | Columbus NanoWorks (United States), Tokyo Denki University |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: Optical Spin Polarization in NV(-) Diamond Centers
Section titled “Technical Analysis and Documentation: Optical Spin Polarization in NV(-) Diamond Centers”Executive Summary
Section titled “Executive Summary”This research validates the use of Electron Paramagnetic Resonance (EPR) under optical spin polarization (OSP) conditions as a critical diagnostic tool for selecting high-quality synthetic diamond material suitable for quantum applications.
- Core Achievement: Demonstrated significant amplification of EPR signals corresponding to Nitrogen-Vacancy (NV-) centers in synthetic Ib HPHT diamond microcrystals under broadband illumination at cryogenic temperatures (90-100 K).
- Signal Enhancement: The intensity of “allowed” (Δms = 1) transitions was amplified by a factor of 5-6x, while “forbidden” (Δms = 2) transitions were amplified by 2.5-3x, confirming successful optical spin polarization.
- Material Quality Validation: High crystalline quality was confirmed by a narrow Raman line (3.4 cm-1 FWHM) and the absence of mechanical strains, a prerequisite for high-coherence quantum sensing.
- Defect Engineering: The material was engineered to achieve an optimal NV- concentration (~3.8 ppm) while maintaining a high substitutional nitrogen background (140 ± 10 ppm) and low nickel impurity content (< 5 ppm).
- Application Relevance: The OSP effect provides a non-destructive method to select diamond microcrystals with excellent technical characteristics, including high luminescence brightness and low internal stresses, essential for single-photon sources and quantum sensors.
- Methodology: NV- centers were created via high-energy electron irradiation (> 2 MeV) followed by high-temperature annealing (800 °C) and subsequent milling and surface etching (450 °C oxidation).
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the experimental procedures and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Type | Synthetic Ib HPHT | N/A | Starting material |
| Initial Crystal Size | 200-350 | µm | Before milling |
| Final Particle Size (Range) | 4-35 | µm | Average size ~13 µm |
| Substitutional Nitrogen (P1) | 140 ± 10 | ppm | Main dopant concentration |
| NV(-) Center Concentration | ~3.8 | ppm | Target defect concentration |
| Impurity Nickel Content | < 5 | ppm | Measured at 4.3 ppm |
| Electron Irradiation Dose | ~ 6 x 1018 | e-/cm2 | NV(-) creation step |
| Annealing Temperature | 800 | °C | Post-irradiation processing (6 hours) |
| Etching Temperature | 450 | °C | Gas-phase oxidation for sp2 removal (1 hour) |
| EPR Measurement Temperature | 90-100 | K | Cryogenic operating range |
| Temperature Stabilization | 0.03 | K | High precision required for measurement |
| Microwave Frequency (X-band) | ~ 9.081 | GHz | EPR operating frequency |
| Raman Line Width (FWHM) | 3.4 | cm-1 | Indicator of low lattice strain |
| NV(-) ZPL Wavelength | 638 | nm | Zero-Phonon Line |
| Maximum Signal Amplification | 5-6 | Times | Allowed (Δms = 1) transitions under OSP |
Key Methodologies
Section titled “Key Methodologies”The material preparation and characterization relied on precise defect engineering and high-resolution spectroscopy:
- HPHT Growth: Microcrystals were synthesized under high pressures (> 5 GPa) and high temperatures (> 1300 °C) using a nickel-containing metal catalyst.
- Defect Introduction: NV- centers were created by high-energy electron irradiation (> 2 MeV) to generate vacancies.
- Thermal Treatment: Subsequent annealing at 800 °C for 6 hours in an inert atmosphere facilitated vacancy migration and NV center formation.
- Mechanical Processing: The crystals were powdered in a planetary mill to achieve microcrystal sizes (4-35 µm) suitable for ensemble studies and fiber integration.
- Surface Cleaning: Powders were subjected to boiling acid cleaning to remove metal contaminants, followed by gas-phase etching (oxidation at 450 °C) to remove surface sp2 carbon defects.
- EPR Spectroscopy: Measurements were conducted at 90-100 K using a JEOL-JES-FA300 spectrometer operating at ~9.081 GHz, equipped with a flow-type cryostat and optical window.
- Optical Spin Polarization (OSP): Broadband illumination from a 500 W xenon lamp was applied, often filtered (e.g., L42 filter, λ ≥ 420 nm), to selectively excite the NV- centers and induce spin polarization in the ground state sublevels.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The successful replication and extension of this research—particularly the need for high-quality, low-strain diamond with precisely controlled defect concentrations—is directly supported by 6CCVD’s advanced MPCVD capabilities.
Applicable Materials
Section titled “Applicable Materials”To achieve the high crystalline quality and specific defect concentrations required for efficient optical spin polarization and quantum sensing, 6CCVD recommends:
- Optical Grade Single Crystal Diamond (SCD): For applications requiring the highest coherence times, lowest strain, and precise control over individual NV centers. 6CCVD offers SCD up to 500 µm thick.
- High-Purity Polycrystalline Diamond (PCD): For large-area ensemble sensing applications where high NV- concentration across a large wafer (up to 125 mm diameter) is necessary. Our PCD exhibits excellent lattice quality suitable for high-yield NV creation.
- Custom Nitrogen Doping: 6CCVD can precisely control nitrogen incorporation during MPCVD growth to achieve the required substitutional nitrogen (P1) concentration (e.g., 140 ppm) necessary for subsequent NV- formation via irradiation and annealing.
Customization Potential
Section titled “Customization Potential”The research utilized specific dimensions (microcrystals) and required rigorous post-processing. 6CCVD provides comprehensive customization services:
| Requirement from Paper | 6CCVD Customization Capability | Benefit to Researcher |
|---|---|---|
| Microcrystal Dimensions (4-35 µm) | Custom Laser Cutting & Milling: We process SCD/PCD wafers into specific shapes, sizes, or powders. | Enables integration into fiber optics or micro-sensor arrays. |
| High-Energy Irradiation | Post-Growth Processing Support: We partner with specialized facilities to manage electron irradiation and subsequent high-temperature annealing (800 °C). | Ensures optimal NV- yield and charge state stability. |
| Ultra-Low Strain Lattice | Advanced Polishing: SCD polishing to Ra < 1 nm; Inch-size PCD polishing to Ra < 5 nm. | Minimizes spectral diffusion and maximizes ZPL stability, critical for OSP efficiency. |
| Metal Impurity Control | High-Purity MPCVD Growth: Our process minimizes transition metal incorporation (< 5 ppm Ni in the paper). | Reduces unwanted paramagnetic background signals (Ni-, P1 centers) that interfere with NV- EPR detection. |
| Integrated Devices | Custom Metalization: In-house deposition of Au, Pt, Pd, Ti, W, and Cu stacks. | Facilitates the creation of integrated quantum devices, including microwave antennas for ODMR/EPR experiments. |
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team specializes in material science for quantum technologies. We offer expert consultation to assist researchers in similar Quantum Sensing and Spin Polarization projects:
- Material Recipe Optimization: Guidance on selecting the optimal starting material (SCD vs. PCD) and nitrogen doping levels to maximize NV- concentration and OSP efficiency.
- Post-Processing Protocol: Assistance in designing and executing post-growth treatments (irradiation dose, annealing temperature/duration, surface etching) to ensure the desired NV- charge state (> 98% NV-) and low internal stress.
- Global Logistics: We ensure reliable global shipping (DDU default, DDP available) for sensitive, custom-engineered diamond materials.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Electron paramagnetic resonance (EPR) spectra of synthetic diamond microcrystals with NV (-) -centers have been studied. It is shown that under the conditions of irradiation of the material with the light of a xenon lamp at low temperatures ~ 100 K, the intensities of the EPR signals corresponding to the &quot;forbidden&quot; (Delta m s =2) and low field allowed (Delta m s =1) transitions are amplified several times, while the EPR signals from paramagnetic nitrogen and impurity nickel in the charge state -1 practically do not change. This is due to a change in the population of levels of the ground triplet state of the NV (-) - center and the optical polarization of spins in the state m s =0 of the triplet level. Keywords: nitrogen-vacancy centers, synthetic diamond, electron paramagnetic resonance, spin polarization, luminescence.