Wide-field strain imaging with preferentially aligned nitrogen-vacancy centers in polycrystalline diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-12-19 |
| Journal | New Journal of Physics |
| Authors | Matthew E. Trusheim, Dirk Englund |
| Citations | 69 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Wide-Field Strain Imaging via NV Centers in PCD
Section titled âTechnical Documentation & Analysis: Wide-Field Strain Imaging via NV Centers in PCDâExecutive Summary
Section titled âExecutive SummaryâThis research validates MPCVD Polycrystalline Diamond (PCD) as a scalable, high-performance platform for quantum sensing applications, specifically wide-field, 3D strain mapping using Nitrogen-Vacancy (NV) centers.
- PCD Viability Confirmed: Polycrystalline diamond exhibits long spin coherence times (T2) comparable to single-crystal diamond (SCD), confirming its suitability as a cost-effective, wafer-scale material for quantum sensors.
- High Sensitivity Strain Imaging: The ODMR technique achieved diffraction-limited spatial resolution and exceptional strain sensitivity (< 10-5 Hz-1/2, or < 10 MPa equivalent pressure).
- 3D Characterization: The methodology successfully mapped axial and non-axial strain components (Ez and Eâ„) in three dimensions, revealing strain gradients that relax over distances of 10-24 ”m from grain boundaries.
- Preferential NV Alignment: Natural preferential alignment of NV centers was observed within certain PCD grains, which is predicted to yield a fourfold improvement in optically detected magnetic resonance (ODMR) contrast.
- Extreme Stress Environment: Internal strain gradients approaching 6 * 10-4 axial strain (corresponding to internal pressures > 1 GPa) were observed, demonstrating PCDâs utility for studying quantum devices in extreme operational regimes.
- 6CCVD Value Proposition: 6CCVD offers the necessary wafer-scale, low-nitrogen PCD materials, precision polishing (Ra < 5 nm), and custom metalization capabilities essential for replicating and scaling this wide-field sensing technology.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key performance metrics and material properties extracted from the wide-field strain imaging study.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| PCD Material Type | IIa | N/A | CVD Polycrystalline Diamond |
| Nitrogen Concentration | < 50 | ppb | Ultra-low concentration for long T2 |
| NV Density Range | 0.1 to 1.0 | NV/”m2 | Spatially heterogeneous density observed |
| Axial Strain Maximum | 6 * 10-4 | Unitless | Observed near grain boundaries (> 1 GPa) |
| Non-Axial Strain Maximum | 1.8 * 10-4 | Unitless | Observed near grain boundaries |
| Axial Strain Precision | 2.7 * 10-5 | Unitless | Per-pixel measurement precision |
| Non-Axial Strain Precision | 1.2 * 10-5 | Unitless | Per-pixel measurement precision |
| Axial Strain Sensitivity (Best Case) | 1.02 * 10-4 | Hz-1/2 | Focus on high-SNR regions |
| Non-Axial Strain Sensitivity (Best Case) | 4.7 * 10-5 | Hz-1/2 | Focus on high-SNR regions |
| ODMR Spectral Resolution | 245 | kHz | Median per-pixel resolution |
| Spatial Resolution | Diffraction-limited | N/A | Achieved via wide-field ODMR |
| Field of View (Imaging) | > 300 | ”m2 | Used for wide-field ODMR spectroscopy |
| Depth Resolution (3D Mapping) | 1 | ”m | Vertical offset for sectional imaging |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on specific material properties and a custom-built wide-field optically detected magnetic resonance (ODMR) setup utilizing precise control over optical, microwave, and magnetic fields.
- Material Selection: Type IIa polycrystalline diamond grown by MPCVD (Element6) was selected for its low nitrogen concentration (< 50 ppb) to ensure high T2 coherence times.
- Optical Excitation: A 532 nm green laser, modulated by a double-pass acousto-optic modulator, was used for NV illumination.
- Fluorescence Collection: NV fluorescence (650 nm long-pass filtered) was collected onto an electron-multiplying CCD camera for wide-field imaging.
- Microwave (MW) Manipulation: Spin manipulation was achieved by applying microwave-frequency excitation via a 15 ”m copper wire placed near the diamond surface.
- Magnetic Field Control: Three orthogonal current-controlled electromagnets, supplemented by a permanent rare-earth magnet, controlled the static magnetic field B.
- Low-Field ODMR: Strain mapping was performed in the low magnetic field regime (Bz << Eâ„) by actively canceling external magnetic fields using the electromagnets, maximizing NV sensitivity to local strain.
- 3D Mapping: Strain mapping in the diamond bulk was achieved by varying the depth of focus, allowing for sectional imaging and 3D reconstruction of axial (Ez) and non-axial (Eâ„) strain profiles.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and precision engineering services required to replicate, scale, and optimize this cutting-edge quantum sensing research. The paper highlights the potential of PCD for wafer-scale applications, a primary strength of 6CCVD.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the long T2 coherence times and high sensitivity required for NV strain imaging, researchers must start with ultra-pure, low-nitrogen diamond.
| Application Requirement | 6CCVD Material Solution | Specification Match |
|---|---|---|
| Wide-Field Strain Sensing | Ultra-Low N PCD Wafers | CVD Polycrystalline diamond optimized for low < 5 ppb N concentration (Type IIa equivalent) to maximize T2 coherence time, crucial for sensing sensitivity (Hz-1/2). |
| Reference & Benchmarking | High-Purity SCD Plates | Single-Crystal Diamond (SCD) material, necessary for developing homogeneous NV layers and providing a low-strain reference for absolute calibration. SCD thickness available from 0.1 ”m up to 500 ”m. |
| Integrated Quantum Devices | Optical Grade Polished PCD | PCD substrates with polishing specified to Ra < 5 nm across inch-size wafers, directly addressing the device performance limitations (roughness and scattering) cited in the research. |
Customization Potential
Section titled âCustomization PotentialâThe current work uses a 15 ”m copper wire placed on the surface for microwave delivery. Scaling this application to integrated photonic circuits or large-area sensors requires robust, customized metalization and substrate dimensions.
- Wafer-Scale Substrates: The paper emphasizes PCDâs advantage for large areas. 6CCVD routinely provides PCD plates/wafers up to 125mm in diameter, enabling true wafer-scale manufacturing of wide-field quantum sensors.
- Integrated Microwave Structures: 6CCVD offers in-house custom metalization (e.g., Ti/Pt/Au, Cu) patterning directly onto the diamond surface. This capability allows for the creation of high-fidelity transmission lines and antennae required for optimal MW delivery and magnetic field control in complex wide-field ODMR setups.
- Custom Dimensions and Thin Films: We provide customizable thicknesses for PCD films (0.1 ”m to 500 ”m) and substrate thicknesses up to 10 mm, critical for optimizing depth profiling and integration into mechanical or photonic devices.
Engineering Support
Section titled âEngineering SupportâThe observed preferential NV alignment and severe strain gradients near grain boundaries in PCD require careful material selection and pre-characterization for device design.
6CCVDâs in-house PhD team specializes in CVD diamond growth physics and defect engineering. We provide expert assistance with:
- Material Selection for Quantum Sensing: Consulting on the optimal nitrogen incorporation recipe to balance NV concentration (0.1 to 1 NV/”m2) against desired T2 coherence time for similar wide-field strain imaging and high-pressure projects.
- Strain Mitigation and Control: Advising on the use of single-crystal versus large-grain PCD to minimize strain inhomogeneity, or alternatively, supplying pre-characterized high-strain PCD testbeds for extreme operational regime experiments (pressures > 1 GPa).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We report on wide-field optically detected magnetic resonance imaging of nitrogen-vacancy centers (NVs) in type IIa polycrystalline diamond. These studies reveal a heterogeneous crystalline environment that produces a varied density of NV centers, including preferential orientation within some individual crystal grains, but preserves long spin coherence times. Using the native NVs as nanoscale sensors, we introduce a 3-dimensional strain imaging technique with high sensitivity ( $< 10^{-5}$ Hz$^{-1/2}$) and diffraction-limited resolution across a wide field of view.