Wide-Field Dynamic Magnetic Microscopy Using Double-Double Quantum Driving of a Diamond Defect Ensemble
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-05-14 |
| Journal | Physical Review Applied |
| Authors | Zeeshawn Kazi, Isaac M. Shelby, Hideyuki Watanabe, Kohei M. Itoh, V. Shutthanandan |
| Institutions | Environmental Molecular Sciences Laboratory, National Institute of Advanced Industrial Science and Technology |
| Citations | 25 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Wide-Field Dynamic Magnetic Microscopy
Section titled âTechnical Documentation & Analysis: Wide-Field Dynamic Magnetic Microscopyâ6CCVD Reference Document: DDQ-MAG-2021-01 Source Paper: Kazi et al., âWide-field dynamic magnetic microscopy using double-double quantum driving of a diamond defect ensembleâ (arXiv:2002.06237v3)
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a significant advancement in wide-field Nitrogen Vacancy (NV) ensemble magnetometry by introducing the Double-Double Quantum (DDQ) driving technique. This method directly addresses the primary limitation of large-area NV sensors: spatial inhomogeneities.
- Core Innovation: DDQ driving utilizes four-tone radio frequency (RF) pulses to suppress variations in the NV resonance curve shape (contrast $C$ and linewidth $\delta\nu$) across the imaging field of view.
- Inhomogeneity Mitigation: The technique eliminates non-magnetic perturbations (strain, temperature, electric field) and curve-shape variations, enabling robust, absolute magnetic field projection mapping without prior per-pixel calibration.
- High-Speed Dynamic Imaging: DDQ facilitates high-frame-rate magnetic microscopy, achieving 15.6 Hz (64 ms exposure time) imaging of dynamic fields, suitable for single-molecule biophysics applications.
- Performance Gain: The DDQ modality provides similar magnetic sensitivity to traditional static frequency scanning methods but achieves a greater than four-fold reduction in acquisition time.
- Material Requirements: Success relies critically on a high-quality, near-surface 15N-doped NV ensemble layer (150 nm thick) grown on an ultra-pure, electronic-grade 12C diamond substrate (99.999% purity) to maximize spin coherence time (T2 = 2.5 ”s).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental methods and results sections, highlighting the material and performance metrics achieved.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Layer Thickness | 150 | nm | 15N doped, 12C purified layer |
| 12C Isotope Purity | 99.999 | % | Required for long T2 coherence time |
| NV Ensemble Density | 1.7 x 1016 | cm-3 | High density required for ensemble sensing |
| Ensemble Spin Coherence Time (T2) | 2.5 | ”s | Achieved T2 time |
| He+ Implantation Energy | 25 | keV | Used for vacancy creation |
| He+ Implantation Dose | 5 x 1011 | ions/cm2 | Used for vacancy creation |
| NV Formation Anneal Temperature | 900 | °C | Vacuum anneal duration: 2 h |
| Charge State Stabilization Temp | 425 | °C | O2 anneal duration: 2 h |
| External Static Magnetic Field (Bext) | 1 | mT | Applied along the <111> NV orientation |
| Average Volume Normalized Sensitivity | 31 | nT Hz-1/2 ”m3/2 | Achieved sensitivity in the magPI platform |
| Dynamic Imaging Frame Rate | 15.6 | Hz | Corresponds to 64 ms exposure time per frame |
| RF Tone Separation (Hyperfine) | 3.05 | MHz | Used for simultaneous driving of 15N-NV transitions |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on precise material engineering and advanced quantum control sequences to achieve high-fidelity wide-field imaging.
- Material Growth: A 150 nm thick layer of 15N doped, isotope-purified (99.999% 12C) diamond was grown via Chemical Vapor Deposition (CVD) on an electronic-grade diamond substrate.
- Vacancy Creation: The sample was implanted with 25 keV He+ ions at a dose of 5 x 1011 ions/cm2 to introduce vacancies near the surface.
- Annealing Protocol: Sequential annealing was performed: 900 °C in vacuum (2 h) for NV formation, followed by 425 °C in O2 (2 h) for charge state stabilization.
- Optical Pumping: A 532 nm laser pulse was used to initialize the NV ensemble into the |ms = 0> ground state.
- RF Excitation (DDQ): Four-tone RF Ï-pulses were applied simultaneously via a broadband microwave antenna. The tones were positioned at the outer (f1, f4) and inner (f2, f3) inflection points of the two Zeeman-split resonance curves.
- Readout: The photoluminescence (PL) intensity reduction was monitored using a sCMOS camera during pulsed excitation sequences (4 ms total duration).
- Data Processing: The DDQ difference image (DDQ DI) was constructed using only two images, $I_{on}(f_{1}, f_{4})$ and $I_{on}(f_{2}, f_{3})$, enabling high-frame-rate mapping of the magnetic field projection $\mathbf{B} - \langle\mathbf{B}\rangle$.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful implementation of DDQ dynamic magnetometry requires diamond substrates with exceptional purity, precise doping profiles, and high surface qualityâall core competencies of 6CCVDâs MPCVD manufacturing.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research, 6CCVD recommends the following materials:
| Application Requirement | 6CCVD Material Recommendation | Technical Rationale |
|---|---|---|
| High Coherence Time (T2) | Isotopically Pure Single Crystal Diamond (SCD) | Guaranteed 12C purity (>99.999%) minimizes spin bath noise, essential for achieving the T2 = 2.5 ”s required for high-fidelity quantum control sequences like DDQ. |
| Near-Surface High-Density NV Layer | Custom 15N Doped SCD | We offer precise control over nitrogen doping during CVD growth, allowing for the creation of high-density 15N ensembles (1.7 x 1016 cm-3) necessary for ensemble sensing sensitivity. |
| Wide-Field Imaging Platform | Large Format Polycrystalline Diamond (PCD) | For scaling the wide-field platform beyond typical SCD sizes, 6CCVD offers PCD plates up to 125 mm diameter, suitable for large-area sensor integration. |
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs in-house engineering capabilities directly address the specific fabrication and integration challenges presented in this work:
- Custom Dimensions and Thickness: The paper utilized a 150 nm sensing layer. 6CCVD provides custom SCD thicknesses from 0.1 ”m up to 500 ”m, allowing researchers to optimize the NV depth for specific magnetic field gradients (e.g., nanoscale vs. bulk fields). We also supply substrates up to 10 mm thick.
- Precision Polishing: Achieving reliable bio-integration (DNA tethering) and minimizing optical scattering requires an ultra-smooth surface. 6CCVD guarantees Ra < 1 nm polishing for SCD, ensuring optimal surface quality for sensitive microscopy.
- RF Integration and Metalization: The DDQ technique relies on efficient delivery of four-tone RF pulses via a microwave antenna. 6CCVD offers internal metalization services (Au, Pt, Pd, Ti, W, Cu) to fabricate custom antenna structures directly onto the diamond surface, facilitating robust quantum control.
- Post-Processing Advisement: While the paper used He+ implantation, 6CCVDâs PhD team can advise on optimizing CVD growth parameters or post-processing recipes (implantation dose and annealing protocols) to achieve the target NV density and charge state stability (900 °C and 425 °C anneals).
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in defect engineering and material optimization for quantum sensing. We can assist with material selection for similar dynamic magnetic microscopy projects, ensuring the substrate properties (purity, strain, doping) are perfectly matched to the demanding requirements of high-speed, inhomogeneity-mitigated quantum control sequences like DDQ.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Wide-field magnetometry can be realized by imaging the optically-detected magnetic resonance of diamond nitrogen vacancy (NV) center ensembles. However, NV ensemble inhomogeneities significantly limit the magnetic-field sensitivity of these measurements. We demonstrate a double-double quantum (DDQ) driving technique to facilitate wide-field magnetic imaging of dynamic magnetic fields at a micron scale. DDQ imaging employs four-tone radio frequency pulses to suppress inhomogeneity-induced variations of the NV resonant response. As a proof-of-principle, we use the DDQ technique to image the dc magnetic field produced by individual magnetic-nanoparticles tethered by single DNA molecules to a diamond sensor surface. This demonstrates the efficacy of the diamond NV ensemble system in high-frame-rate magnetic microscopy, as well as single-molecule biophysics applications.