Frequency modulation technique for wide-field imaging of magnetic field with nitrogen-vacancy ensembles
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-02-10 |
| Journal | Japanese Journal of Applied Physics |
| Authors | Yukihiro Miura, Satoshi Kashiwaya, Shintaro Nomura |
| Institutions | University of Tsukuba, National Institute of Advanced Industrial Science and Technology |
| Citations | 6 |
| Analysis | Full AI Review Included |
6CCVD Technical Analysis: Wide-Field NV Magnetometry using Frequency Modulation
Section titled â6CCVD Technical Analysis: Wide-Field NV Magnetometry using Frequency ModulationâReference Paper: Miura, Kashiwaya, & Nomura. âFrequency modulation technique for wide-field imaging of magnetic field with nitrogen-vacancy ensembles.â (JJAP Regular Papers)
Executive Summary
Section titled âExecutive SummaryâThis paper presents a robust method for highly efficient, wide-field magnetic field imaging utilizing Nitrogen-Vacancy (NV) ensembles in Single Crystal Diamond (SCD) via Optically Detected Magnetic Resonance (ODMR).
- Core Achievement: Demonstrated wide-field magnetic field imaging using frequency modulation (FM) ODMR, significantly reducing total image acquisition time compared to traditional scanning probe techniques.
- Time Reduction: Wide-field imaging of a $35 \times 34\text{ ”m}$ area was completed in $12\text{ s}$, providing a comparable sensitivity to a scanning probe approach that typically requires $\sim 10\text{ min}$.
- Sensitivity Achieved: A magnetic field sensitivity of $\eta = 21\text{ ”T}/(0.65\text{ ”m})^2/\sqrt{\text{Hz}}$ was obtained, projected to improve to $2\text{ ”T}/(0.65\text{ ”m})^2/\sqrt{\text{Hz}}$ through optimization.
- Material Basis: Required high-purity, (100)-oriented CVD Single Crystal Diamond (SCD) with native nitrogen concentration less than $5\text{ ppb}$.
- NV Formation: NV centers were created via precise low-energy $^{15}\text{N}_{2}^{+}$ ion implantation followed by $800\text{ °C}$ annealing, establishing the material requirements for next-generation quantum sensing devices.
- Technique Advantage: The FM technique offers fast response and requires less complex pulsing resources than Ramsey-type sequences, making it ideal for scalable, wide-field sensor integration.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental setup and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material | SCD (Type IIa) | - | (100)-oriented, CVD-grown |
| Nominal Dimensions | $2.0 \times 2.0 \times 0.5$ | $\text{mm}^{3}$ | Chip size used for experiment |
| Native N Concentration | < 5 | $\text{ppb}$ | Ultra-low requirement for high $T_{2}^{*}$ coherence |
| Ion Implantation | $^{15}\text{N}_{2}^{+}$ | Ion | Source for NV creation |
| Implantation Energy | 10 | $\text{keV}$ | Controls depth and spatial localization |
| Implantation Fluence | $1 \times 10^{13}$ | $\text{cm}^{-2}$ | Density of introduced nitrogen |
| Annealing Temperature | 800 | $\text{°C}$ | Used for NV center formation |
| Excitation Wavelength | 520 | $\text{nm}$ | Green laser source |
| Excitation Power | 6.5 | $\text{mW}$ | Power incident on microscope objective |
| Microwave Power | 17 | $\text{dBm}$ | Delivered via single-turn coil |
| FM Modulation Rate ($r_{\text{mod}}$) | 20 | $\text{Hz}$ | Limited by sCMOS frame rate |
| FM Modulation Amplitude ($f_{\text{mod}}$) | 1 | $\text{MHz}$ | Used for frequency modulation |
| Achieved Sensitivity ($\eta$) | 21 | $\text{”T}/(0.65\text{ ”m})^{2}/\sqrt{\text{Hz}}$ | Achieved using FM ODMR at $2.747\text{ GHz}$ |
| Projected Sensitivity Target | 2 | $\text{”T}/(0.65\text{ ”m})^{2}/\sqrt{\text{Hz}}$ | Optimized target by improving contrast/linewidth |
| Spatial Resolution Limit | 0.65 | $\text{”m}$ | Limited by camera pixel size |
| Wide-Field Acquisition Time | 12 | $\text{s}$ | For $528 \times 512\text{ pixels}$ image |
Key Methodologies
Section titled âKey MethodologiesâThe experimental success relied on tight control over material purity, NV creation parameters, and the integration of the microwave delivery system.
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Material Preparation:
- Selected (100)-oriented, CVD-grown Single Crystal Diamond (SCD) with exceptionally high purity (Type IIa, native N < $5\text{ ppb}$) to maximize spin coherence time ($T_{2}^{*}$).
- The diamond chip was sized at $2.0 \times 2.0 \times 0.5\text{ mm}$.
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NV Center Generation:
- $^{15}\text{N}_{2}^{+}$ ions were implanted at $10\text{ keV}$ energy and a fluence of $1\times 10^{13}\text{ cm}^{-2}$.
- The chips were subsequently annealed at $800\text{ °C}$ for $30\text{ min}$ to mobilize vacancies, allowing them to bind with implanted nitrogen atoms to form the $\text{NV}^{-}$ centers.
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Microwave (MW) Integration:
- A single-turn coil ($1\text{ mm}$ diameter, $50\text{ ”m}$ width) was fabricated on a sapphire substrate using photolithography.
- This coil was placed directly onto the diamond chip to deliver the high-power (17 dBm) microwave signal necessary for magnetic resonance.
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Optical and Detection Setup:
- Optical excitation was provided by a $520\text{ nm}$ stabilized semiconductor laser diode ($6.5\text{ mW}$).
- Photoluminescence (PL) was collected using a $100\times$, NA $0.73$ objective.
- A long-wavelength pass filter (cut-on $650\text{ nm}$) was used to isolate the NV center fluorescence from the excitation light.
- PL imaging was performed in parallel using a cooled scientific CMOS (sCMOS) camera, achieving a spatial resolution limit of $0.65\text{ ”m}$.
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Frequency Modulation (FM) ODMR:
- The microwave frequency was modulated rectangularly ($f(t) = f_{0} \pm f_{\text{mod}}$) at a rate of $20\text{ Hz}$.
- This technique yields a signal proportional to the first derivative of the ODMR spectrum, significantly improving the signal-to-noise ratio and hence the magnetic field sensitivity in the wide-field configuration.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical reliance on high-quality, ultra-pure SCD substrates for advanced quantum sensing applications like wide-field NV magnetometry. 6CCVD is an expert supplier ready to meet and exceed the demanding specifications outlined in this paper.
Applicable Materials for Replication and Scaling
Section titled âApplicable Materials for Replication and ScalingâTo replicate or advance this research, 6CCVD recommends materials optimized for quantum sensing performance:
| Material Specification | 6CCVD Material Designation | Relevance to Research |
|---|---|---|
| Ultra-Low Native N Substrates | Electronic Grade SCD | Essential for maximizing the inhomogeneous dephasing time ($T_{2}^{*}$) and achieving high magnetic field sensitivity (required N concentration < $5\text{ ppb}$). |
| Doped Ensembles (NV Creation) | $^{15}\text{N}$ Doped SCD Wafers | For highly uniform, shallow NV ensembles (required for surface applications). We can supply SCD grown using $^{15}\text{N}$ precursor gas to achieve precise, homogeneous doping concentrations that often surpass the uniformity of ion implantation. |
| High Surface Quality | Optical Grade SCD Wafers | The paper utilizes high-NA optical collection; 6CCVD guarantees surface polishing down to $\text{Ra} < 1\text{ nm}$ for SCD, critical for maximizing PL collection efficiency. |
Customization Potential for Integrated Sensing Systems
Section titled âCustomization Potential for Integrated Sensing SystemsâThe successful operation of the device requires integration of the microwave delivery coil, which presents specific engineering challenges that 6CCVD can solve:
- Custom Dimensions and Orientation: We offer (100)-oriented SCD chips up to $125\text{ mm}$ size, allowing for significant scaling of the $2.0 \times 2.0 \times 0.5\text{ mm}$ chips used in the study.
- Precision Thickness Control: We provide SCD substrates with precise thickness control from $0.1\text{ ”m}$ up to $500\text{ ”m}$ (and substrates up to $10\text{ mm}$), enabling optimal laser penetration and NV ensemble depth matching.
- Integrated Metalization (MW Coils): The paper utilized an external coil structure. For next-generation integrated quantum sensors, 6CCVD provides in-house metalization services, including $\text{Au, Pt, Pd, Ti, W, and Cu}$. This capability allows researchers to pattern the necessary single-turn or antenna structures directly onto the diamond surface or the sapphire carrier, simplifying device assembly and improving MW coupling efficiency.
- Laser Machining: We offer custom laser cutting services to shape substrates or pattern complex surface features to accommodate highly localized optical and electrical components.
Engineering Support & Global Logistics
Section titled âEngineering Support & Global Logisticsâ6CCVDâs in-house team of PhD material scientists and technical engineers specializes in optimizing MPCVD growth and post-processing treatments (like polishing and metalization) for specific quantum applications. We can assist researchers in material selection, NV creation optimization (whether via implantation or in-situ doping), and structural design for similar Wide-Field Quantum Sensing and Solid-State Characterization projects.
We offer global shipping (DDU default, DDP available) to ensure rapid and reliable delivery of custom diamond solutions worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We report on the application of a frequency modulation technique to wide-field magnetic field imaging of nitrogen-vacancy centers in diamond at room temperature. We use a scientific CMOS (sCMOS) camera to collect photoluminescence images from a large number of nitrogen-vacancy center ensembles in parallel. This technique allows a significant reduction in the measurement time required to obtain a magnetic field image compared with a scanning probe approach at a comparable magnetic field sensitivity.