Sub-second temporal magnetic field microscopy using quantum defects in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-05-24 |
| Journal | Scientific Reports |
| Authors | Madhur Parashar, Anuj Bathla, Dasika Shishir, Alok Gokhale, Sharba Bandyopadhyay |
| Institutions | Indian Institute of Technology Bombay, Indian Institute of Technology Kharagpur |
| Citations | 29 |
| Analysis | Full AI Review Included |
Dynamic Widefield NV Magnetometry: Sub-second Temporal Magnetic Field Microscopy
Section titled âDynamic Widefield NV Magnetometry: Sub-second Temporal Magnetic Field MicroscopyâThis technical documentation analyzes the requirements and achievements of the research paper âSub-second temporal magnetic field microscopy using quantum defects in diamondâ and maps them directly to the advanced material solutions and engineering capabilities offered by 6CCVD.
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a significant breakthrough in diamond-based quantum sensing, achieving dynamic magnetic field imaging at millisecond timescales. The core value proposition for 6CCVD clients is the ability to move beyond static magnetic field mapping into real-time observation of microscale phenomena.
- High-Speed Imaging: Achieved dynamic widefield magnetic field imaging at frame rates ranging from 50 to 200 frames per second (fps), a substantial improvement over conventional static ODMR methods (minutes per frame).
- Enhanced Sensitivity: Utilized a novel per-pixel lock-in detection protocol synchronized with frequency-modulated optically detected magnetic resonance (fm-ODMR).
- Performance Metric: Measured a median per-pixel magnetic field sensitivity of 731 nT/â(Hz).
- Material Requirement: Relied on high-quality, isotopically pure Single Crystal Diamond (SCD) with a shallow, high-density Nitrogen Vacancy (NV-) implanted layer (1 ”m depth, 1-2 ppm concentration).
- Application Potential: Enables new applications in quantum materials research, vortex dynamics in superconductors, and high-speed bio-magnetometry (e.g., tracking magnetic nanoparticles in living cells).
- 6CCVD Relevance: The success of this technique is fundamentally dependent on the quality and customization of the SCD substrate and associated metalization, both of which are core 6CCVD specialties.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, highlighting the performance achieved using the diamond NV platform.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Dynamic Imaging Frame Rate | 50 - 200 | fps | Achieved via per-pixel lock-in detection |
| Median Magnetic Field Sensitivity | 731 | nT/â(Hz) | Median per-pixel sensitivity across the FOV |
| Diamond Material Type | Isotopically Pure SCD | N/A | Procured from Element Six |
| Crystal Dimensions (Lateral x Thickness) | 4.5 x 4.5 x 0.5 | mm | Substrate dimensions |
| NV- Layer Depth | 1 | ”m | Shallow implanted layer |
| NV- Concentration | 1 - 2 | ppm | Nitrogen Vacancy concentration |
| Spatial Resolution (Microwire) | 1.33 | ”m/pixel | Limited by NV layer standoff (~13 ”m) |
| Spatial Resolution (Microcoil) | 1.7 | ”m/pixel | Limited by NV layer standoff (~14 ”m) |
| MW Frequency Range | 2.5 - 3.2 | GHz | Applied resonant frequencies for ODMR |
| Excitation Wavelength | 532 | nm | Continuous green laser illumination |
Key Methodologies
Section titled âKey MethodologiesâThe dynamic widefield magnetic microscopy technique relies on precise synchronization and material engineering.
- Diamond Substrate Preparation:
- Used 500 ”m thick, isotopically pure Single Crystal Diamond (SCD) with a {100} front facet.
- A thin, high-density NV- layer (1 ”m depth, 1-2 ppm concentration) was created via implantation.
- Microstructure Fabrication:
- Microscale conductive samples (10 ”m track width microwires and spiral microcoils) were fabricated on silicon substrates using e-beam lithography.
- Metalization: 100 nm thick deposition of Titanium/Gold (Ti/Au) was used for the conductive tracks.
- Optical and Microwave Setup:
- Continuous green laser excitation (532 nm, 1.5 W) was focused onto the NV layer via a 100x objective.
- Microwave (MW) resonant frequencies (2.5-3.2 GHz) were applied using frequency shift keying (FSK) waveforms via a loop antenna.
- Lock-in Detection and Synchronization:
- Red photo-luminescence (PL) from the NV centers was collected onto a widefield lock-in camera (Heliotis Helicam C3).
- The cameraâs internal frame acquisition timings were synchronized via external TTL trigger pulses (at 2*omegamod) with the MW modulation frequency (omegamod).
- Signal Processing:
- Per-pixel lock-in detection was performed by integrating light over four quarter periods (S1, S2, S3, S4) and calculating In-phase (I = S1 - S3) and Quadrature (Q = S2 - S4) images.
- Internal averaging (N cycles) was used to enhance the signal-to-noise ratio (SNR) and determine the final imaging frame rate.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe success of high-speed NV magnetometry hinges on the quality and precise engineering of the diamond substrate and its interfaces. 6CCVD is uniquely positioned to supply the materials necessary to replicate and advance this research.
Applicable Materials for Dynamic NV Magnetometry
Section titled âApplicable Materials for Dynamic NV MagnetometryâTo achieve the high SNR and low noise required for sub-second imaging, researchers need the highest quality diamond substrates.
| 6CCVD Material Solution | Specification & Relevance to Research |
|---|---|
| Optical Grade Single Crystal Diamond (SCD) | Required for high-power 532 nm laser excitation and minimal background noise. Our SCD offers low birefringence and high purity, crucial for maximizing NV coherence time and PL contrast. |
| Shallow NV- Substrates | While NV implantation is often performed externally, 6CCVD provides the ideal high-purity SCD substrates (up to 10 mm thick) necessary for subsequent shallow implantation (e.g., 1 ”m depth) and high-density NV creation (1-2 ppm). |
| Polycrystalline Diamond (PCD) Plates | For scaling up widefield imaging applications, 6CCVD offers PCD plates up to 125 mm in diameter, providing a cost-effective path for large-area sensor development, especially where sub-micron spatial resolution is not the primary constraint. |
Customization Potential & Engineering Services
Section titled âCustomization Potential & Engineering ServicesâThe experimental setup required specific dimensions and complex metal microstructures. 6CCVD offers integrated services to streamline the fabrication process for quantum sensing platforms.
- Custom Dimensions and Thickness:
- The paper used 4.5 mm x 4.5 mm x 500 ”m substrates. 6CCVD provides custom-cut SCD plates in various sizes and thicknesses (0.1 ”m to 500 ”m) to perfectly match specific optical setups and objective working distances.
- We offer thick SCD substrates (up to 10 mm) for robust mounting and thermal management under high-power laser illumination (1.5 W used in this study).
- Integrated Metalization Services:
- The microcoils required Ti/Au deposition. 6CCVD offers in-house metalization capabilities, including Ti, Au, Pt, Pd, W, and Cu, allowing researchers to integrate their microstructures directly onto the diamond surface or adjacent substrates with precise control over layer thickness (e.g., 100 nm).
- Ultra-Low Roughness Polishing:
- High-quality surface finish is critical for minimizing scattering and maximizing the collection efficiency of the NV PL. 6CCVD guarantees Ra < 1 nm polishing for SCD, ensuring optimal optical performance for widefield microscopy.
- Engineering Support:
- 6CCVDâs in-house PhD team specializes in material science for quantum applications. We can assist researchers with material selection, orientation ({100} or {111}), and thickness optimization for similar dynamic magnetic field microscopy or nanoscale thermometry projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Wide field-of-view magnetic field microscopy has been realised by probing shifts in optically detected magnetic resonance (ODMR) spectrum of Nitrogen Vacancy (NV) defect centers in diamond. However, these widefield diamond NV magnetometers require few to several minutes of acquisition to get a single magnetic field image, rendering the technique temporally static in itâs current form. This limitation prevents application of diamond NV magnetometers to novel imaging of dynamically varying microscale magnetic field processes. Here, we show that the magnetic field imaging frame rate can be significantly enhanced by performing lock-in detection of NV photo-luminescence (PL), simultaneously over multiple pixels of a lock-in camera. A detailed protocol for synchronization of frequency modulated PL of NV centers with fast camera frame demodulation, at few kilohertz frequencies, has been experimentally demonstrated. This experimental technique allows magnetic field imaging of sub-second varying microscale currents in planar microcoils with imaging frame rates in the range of 50-200 frames per s (fps). Our work demonstrates that widefield per-pixel lock-in detection of frequency modulated NV ODMR enables dynamic magnetic field microscopy.