Microwave-free imaging magnetometry with nitrogen-vacancy centers in nanodiamonds at near-zero field
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-03-03 |
| Journal | Physical Review Applied |
| Authors | Saravanan Sengottuvel, Omkar Dhungel, Mariusz MrĂłzek, Arne Wickenbrock, Dmitry Budker |
| Institutions | GSI Helmholtz Centre for Heavy Ion Research, Helmholtz Institute Mainz |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Microwave-Free NV Magnetometry
Section titled âTechnical Documentation & Analysis: Microwave-Free NV MagnetometryâThis document analyzes the research paper âMicrowave-free imaging magnetometry with nitrogen-vacancy centers in nanodiamonds at near-zero fieldâ to provide technical specifications and highlight how 6CCVDâs advanced MPCVD diamond materials and customization services can replicate, extend, and optimize this cutting-edge research.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a novel, wide-field, microwave-free magnetometry technique utilizing Nitrogen-Vacancy (NV) centers in nanodiamonds (NDs), offering significant advantages for sensitive measurements in complex environments.
- Core Achievement: Demonstrated wide-field magnetic field mapping by exploiting the zero-field cross-relaxation (ZFC) feature of NV centers, eliminating the need for external microwave fields.
- Sensitivity: Achieved a mean per-pixel magnetic field sensitivity of 4.5 ”T/âHz using 140-nm nanodiamond ensembles.
- Application: Successfully visualized the magnetic field generated by a current-carrying copper cross pattern (65 ”m wire width) on a transparent PET substrate.
- Methodology: Utilized a cost-effective âsalt-and-pepperâ drop-casting technique for ND deposition, enabling imaging on arbitrarily shaped surfaces.
- Speed Advantage: Single scans were completed in 2 to 3 minutes, substantially faster than traditional confocal or Atomic Force Microscopy (AFM) scanning methods.
- Critical Limitation Identified: The paper noted that the ZFC feature in NDs exhibited lower contrast (1-2%) and broader linewidth (approx. 2.0 mT) compared to high-concentration single-crystal diamond (SCD) samples, indicating a clear path for material optimization.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental setup and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sensor Material | 140 | nm | Mean size of carboxylated fluorescent nanodiamonds |
| Substrate Thickness (Stand-off) | 0.11 | mm | PET substrate thickness separating NDs from copper pattern |
| Conductive Pattern Width | 65 | ”m | Width of the copper cross pattern wires |
| Applied Current Range | 0 to 0.5 | A | DC current used to generate the magnetic field |
| Background Field Scan Range | -4.0 to +4.0 | mT | Systematic scan range for ZFC measurement |
| Mean Per-Pixel Sensitivity | 4.5 | ”T/âHz | Estimated sensitivity of the ND magnetometer |
| Effective Photon Count Rate | 9 x 106 | counts/s | Used for sensitivity calculation (effective sample area 0.02 ”m2) |
| Zero-Field Feature Contrast (C) | 1 to 2 | % | Observed in nanodiamonds (lower than SCD) |
| Zero-Field Feature Linewidth (w) | ~2.0 | mT | Observed in nanodiamonds (broader than SCD) |
| Camera Field of View (FOV) | 384 x 321 | ”m | Area imaged on the nanodiamond layer |
| Camera Resolution (Per Pixel) | 0.15 x 0.15 | ”m | Spatial resolution of the imaging system |
Key Methodologies
Section titled âKey MethodologiesâThe experiment focused on wide-field, microwave-free magnetometry using the zero-field cross-relaxation (ZFC) feature.
- Nanodiamond Preparation: Commercially available 140-nm carboxylated fluorescent nanodiamonds were suspended in deionized (DI) water and deposited onto a 0.11 mm thick transparent polyethylene terephthalate (PET) substrate via drop-casting.
- Conductive Pattern Integration: A 65 ”m wide copper cross pattern was printed on the reverse side of the PET substrate and connected to a power source to drive current (up to 0.5 A).
- Optical Detection Setup: A home-built wide-field fluorescence microscope was used, employing a 532-nm green LED (60-70 mW) for excitation and a 40x objective (NA 0.65) for collection.
- Magnetic Field Control: A square DC current-carrying coil generated a bias field perpendicular to the NV imaging plane, which was systematically scanned from -4.0 mT to +4.0 mT.
- Data Acquisition: Fluorescence images were captured sequentially using a 12-bit Sony CMOS camera. To improve the signal-to-noise ratio (SNR), 10 scans were averaged (total acquisition time ~20 min).
- Data Analysis: The acquired image data was binned (16 x 16 pixels), and the resulting zero-field cross-relaxation spectrum for each pixel was fitted using a Gaussian function to extract the shift (ÎB), contrast (C), and width (w).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the immense potential of microwave-free NV magnetometry but also points to limitations inherent in using commercial nanodiamonds (low contrast, broad linewidth, stand-off distance). 6CCVD specializes in high-purity MPCVD diamond, offering tailored solutions to overcome these limitations and optimize device performance.
| Research Requirement / Limitation | 6CCVD Material Solution & Capability | Technical Advantage for Replication/Extension |
|---|---|---|
| Low Contrast & Broad Linewidth (Observed in NDs) | Optical Grade Single Crystal Diamond (SCD) (Thickness 0.1 ”m - 500 ”m) | Provides highly controlled, high-concentration NV ensembles, resulting in significantly higher contrast (C) and narrower linewidth (w), directly improving the photon shot-noise-limited sensitivity (ÎŽB â 1/C·Î). |
| Large-Area Wide-Field Imaging | Polycrystalline Diamond (PCD) Plates (Up to 125 mm diameter) | Enables scaling of the wide-field magnetometry system to industrial or large-scale biological applications. We offer PCD polishing to Ra < 5 nm for inch-size plates. |
| Excessive Stand-off Distance (0.11 mm PET substrate) | Ultra-Thin SCD/PCD Substrates (Thickness down to 0.1 ”m) | Allows the NV layer to be placed immediately adjacent to the current source or sample, dramatically reducing the stand-off distance and increasing the detected magnetic field strength (B â 1/r). |
| Non-Uniformity & Drop-Casting Issues | Direct Metalization on Diamond (Au, Pt, Pd, Ti, W, Cu) | We can fabricate the current-carrying cross pattern directly onto the SCD or PCD surface using our in-house metalization capability, ensuring perfect alignment, minimal stand-off, and eliminating the non-uniformity caused by nanodiamond aggregation. |
| Integration into Probes/Tips | Precision Laser Cutting and Shaping | Supports the creation of custom-shaped diamond sensors or substrates required for specialized fiber-coupled probes or integration into existing microscope systems. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers are experts in MPCVD growth and post-processing for quantum sensing applications. We provide comprehensive consultation on material selection, NV creation protocols (e.g., implantation, in-situ doping), and surface preparation (polishing to Ra < 1 nm for SCD) to ensure optimal performance for similar microwave-free magnetometry projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We offer global shipping (DDU default, DDP available) for all custom diamond solutions.
View Original Abstract
Magnetometry using nitrogen-vacancy (N-<a:math xmlns:a=âhttp://www.w3.org/1998/Math/MathMLâ display=âinlineâ overflow=âscrollâ><a:mi>V</a:mi></a:math>) color centers in diamond predominantly relies on microwave spectroscopy. However, microwaves may hinder certain studies involving biological systems or thin conductive samples. This work demonstrates a wide-field, microwave-free imaging magnetometer utilizing N-<d:math xmlns:d=âhttp://www.w3.org/1998/Math/MathMLâ display=âinlineâ overflow=âscrollâ><d:mi>V</d:mi></d:math> centers in nanodiamonds by exploiting the cross-relaxation feature near zero magnetic fields under ambient conditions without applying microwaves. For this purpose, we measure the center shift, contrast, and linewidth of zero-field cross relaxation in 140-nm nanodiamonds dropcast on a current-carrying conductive pattern while scanning a background magnetic field, achieving a sensitivity of <g:math xmlns:g=âhttp://www.w3.org/1998/Math/MathMLâ display=âinlineâ overflow=âscrollâ><g:mn>4.5</g:mn><g:mspace width=â0.1emâ/><g:mtext fontfamily=âtimesâ>ÎŒ</g:mtext><g:mrow><g:mi mathvariant=ânormalâ>T</g:mi></g:mrow><g:mo>/</g:mo><g:msqrt><g:mi>Hz</g:mi></g:msqrt></g:math>. Our work allows for applying the N-<m:math xmlns:m=âhttp://www.w3.org/1998/Math/MathMLâ display=âinlineâ overflow=âscrollâ><m:mi>V</m:mi></m:math> zero-field feature in nanodiamonds for magnetic-field sensing in the zero- and low-field regimes and highlights the potential for microwave-free all-optical wide-field magnetometry based on nanodiamonds.