Wide-field magnetometry using nitrogen-vacancy color centers with randomly oriented micro-diamonds
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-10-26 |
| Journal | Scientific Reports |
| Authors | Saravanan Sengottuvel, Mariusz MrĂłzek, MirosĆaw Sawczak, Maciej J. GĆowacki, Mateusz Ficek |
| Institutions | Polish Academy of Sciences, Jagiellonian University |
| Citations | 23 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research details the development and validation of a simple, low-cost, wide-field magnetometer utilizing Nitrogen-Vacancy (NV) color centers embedded in randomly oriented micro-diamonds.
- Core Innovation: Uses sub-micrometer sized diamond powder deposited in a thin layer on planar or irregular surfaces (via MAPLE), enabling magnetic sensing where conventional bulk diamond or scanning probes are limited.
- Wide-Field Mapping: Achieves simultaneous, parallel mapping of DC magnetic fields over a large field of view (307 x 245 ”m2), significantly faster than sequential scanning methods.
- Vector Magnetometry: Demonstrated the ability to reconstruct the magnetic field vector by analyzing the position and angle dependence of the ODMR resonance pairs from the randomly oriented NV ensembles.
- Automated Analysis: An automated MATLAB algorithm was developed to rapidly extract and fit ODMR spectra from hundreds of diamond spots, estimating magnetic field intensities without human intervention.
- Performance: The system achieved an estimated magnetic field sensitivity of 4.5 ”T/âHz using continuous-wave (cw) ODMR imaging.
- Proof of Concept: Successfully mapped the magnetic field distribution generated by a straight current-carrying wire, confirming agreement between measured and theoretically estimated field values.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Center Material | 1 | ”m | Micro-diamond powder size (MDNV1umHi) |
| Deposition Technique | MAPLE | N/A | Matrix-Assisted Pulsed Laser Evaporation |
| Excitation Wavelength | 530 | nm | Green LED pump beam power: 70 mW |
| Bias Magnetic Field (Bbias) | 3.2 | mT | Applied by neodymium permanent magnet |
| MW Resonance Frequency | 2.87 | GHz | NV ground state transition frequency |
| MW Power Amplifier Gain | +17 | dB | Typical gain at 2800 MHz |
| Current Wire Range | -600 to +600 | mA | DC current applied to MW stripline |
| Estimated Sensitivity (cw-ODMR) | 4.5 | ”T/âHz | Limited by low light intensity and NA |
| Average FWHM (Line Width) | 16 | MHz | Full Width at Half Maximum (power broadened) |
| Field of View (FOV) | 307 x 245 | ”m2 | Area imaged by 40X objective |
| Spatial Resolution (Pixel Area) | (0.24)2 | ”m2 | Area corresponding to one camera pixel |
| Objective Numerical Aperture (NA) | 0.65 | Dimensionless | Used for fluorescence light collection |
| MAPLE Vacuum Condition | 10-5 | mbar | Deposition environment |
| MAPLE Target Temperature | 90-100 | K | Cryogenic temperature of target suspension |
Key Methodologies
Section titled âKey Methodologiesâ- Sample Preparation (MAPLE): Fluorescent micro-diamond powder (sub-1-”m size) was suspended in deionized water. This suspension was cryogenically frozen (90-100 K) to serve as the target for Matrix-Assisted Pulsed Laser Evaporation (MAPLE).
- Thin Film Deposition: Thin films of randomly oriented micro-diamonds were deposited onto planar glass coverslips under high vacuum (10-5 mbar) using a 3225 nm laser, ensuring uniform particle distribution.
- Wide-Field ODMR Setup: The sample was continuously illuminated with a 70 mW, 530 nm green LED pump beam focused by a 40X objective (NA 0.65). Red fluorescence (600-800 nm) was collected and imaged onto a CMOS camera.
- Spin Manipulation and Field Application: A dual copper stripline MW antenna was used to sweep the microwave frequency around 2.87 GHz. A permanent magnet applied a 3.2 mT bias field (Bbias). A DC current (-600 mA to +600 mA) was applied to one stripline to generate the field being mapped.
- Volumetric Data Acquisition: Fluorescence intensity was recorded as a single snapshot for each MW frequency step, creating volumetric image data (2D slices across N frequency frames).
- Automated Spectrum Extraction: An automated MATLAB algorithm identified bright diamond spots, averaged pixel values within each spotâs region, and extracted the complete ODMR spectrum for every micro-diamond simultaneously.
- Vector Field Estimation: The extracted ODMR spectra were fitted to a sum of eight Lorentzians. The resulting resonance frequencies were used to calculate the magnetic field components (Bi, Bj, Bk) relative to the four crystallographic NV axes, enabling vector magnetometry.
- Positional Drift Correction: An algorithm was implemented to correct for thermal positional drift of the diamond spots between successive images by minimizing the distance between identified spots across frames.
Commercial Applications
Section titled âCommercial Applicationsâ- Biomedical and Cellular Imaging: Low-cost, rapid magnetic field mapping for biological systems and living cells, leveraging the ability of nano-diamonds to adhere to irregular surfaces and fiber tips.
- Irregular Surface Sensing: Magnetometry on complex geometries, micro-electromechanical systems (MEMS), or non-planar substrates where conventional scanning probes cannot operate effectively.
- Photonic Sensor Development: Provides a promising path for novel, inexpensive nanodiamond-based photonic sensors for diverse material science and biological applications.
- Micro-Electronics Characterization: Wide-field, high-resolution mapping of current flows and magnetic field distributions in micro-electronic circuits and devices.
- Absolute Vector Magnetometry: Enables the determination of the full 3D magnetic field vector, which is critical for characterizing complex magnetic materials and flux patterns.
View Original Abstract
Abstract Magnetometry with nitrogen-vacancy (NV) color centers in diamond has gained significant interest among researchers in recent years. Absolute knowledge of the three-dimensional orientation of the magnetic field is necessary for many applications. Conventional magnetometry measurements are usually performed with NV ensembles in a bulk diamond with a thin NV layer or a scanning probe in the form of a diamond tip, which requires a smooth sample surface and proximity of the probing device, often limiting the sensing capabilities. Our approach is to use micro- and nano-diamonds for wide-field detection and mapping of the magnetic field. In this study, we show that NV color centers in randomly oriented submicrometer-sized diamond powder deposited in a thin layer on a planar surface can be used to detect the magnetic field. Our work can be extended to irregular surfaces, which shows a promising path for nanodiamond-based photonic sensors.