J2220306 Probe with Nitrogen Vacancy in Diamond Particle for Magnetic Resonance Imaging
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-01-01 |
| Journal | The Proceedings of Mechanical Engineering Congress Japan |
| Authors | Minjie Zhu, Masaya Toda, Takahito Ono |
| Institutions | Tohoku University |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: NV Center Diamond Probe for MRI
Section titled âTechnical Documentation and Analysis: NV Center Diamond Probe for MRIâReference Paper: J2220306: Probe with Nitrogen Vacancy in Diamond Particle for Magnetic Resonance Imaging
Executive Summary
Section titled âExecutive SummaryâThis study successfully demonstrates the fabrication of a diamond-based scanning probe designed for high-sensitivity nanoscale Magnetic Resonance Imaging (MRI). The methodology relies heavily on controlled MPCVD synthesis of diamond microparticles optimized for NV center incorporation.
- Application Focus: Development of a high-sensitivity magnetic sensor probe capable of achieving nanometer spatial resolution, overcoming the conventional limit of tens of ”m in current MRI systems.
- Material Synthesis: Diamond microparticles (1.3-1.5 ”m diameter) were grown using a two-step Microwave Plasma CVD (MPCVD) process, with Nitrogen (Nâ) introduced during the final 0.5 hours to initiate NV center formation.
- Key Process Optimization: Post-synthesis annealing at 1000 °C was determined to be critical. This step eliminated the quenching effect caused by the adsorption of XeFâ gas molecules used for releasing the particles, thereby restoring NV center photoluminescence.
- Structural Integration: Active NV diamond particles were individually selected, picked up using a glass needle, and precision-fixed onto a custom-fabricated silicon cantilever/pillar structure (Deep-RIE etched SOI).
- Confirmation: NV center activity was confirmed via Raman spectroscopy, detecting the photoluminescence peak at 3115 cm-1 (638 nm).
- Core Value Proposition: This method provides a viable and efficient technique for constructing NV-based scanning probes, circumventing the low yield associated with probabilistic NV formation within pre-formed probe tips.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| CVD System Type | ASTeX | N/A | Microwave Plasma CVD (MPCVD) system used for growth. |
| Substrate Size | 20 x 20 | mm | Silicon substrate used for diamond particle deposition. |
| Growth Temperature | 700 | °C | Constant stage temperature during both growth steps. |
| CVD Microwave Power | 1000 | W | Power used for plasma formation. |
| Total Pressure | 6.7 | kPa | Constant chamber pressure. |
| Step 1 Growth Duration | 3.0 | hours | Initial particle growth (Hâ, CHâ only). |
| Step 2 Growth Duration | 0.5 | hours | Nitrogen incorporation (NV center formation). |
| Nitrogen Flow Rate (Step 2) | 0.5 | sccm | Nitrogen gas introduced for NV center creation. |
| Final Particle Diameter | 1.3 - 1.5 | ”m | Size range of deposited diamond particles. |
| Annealing Parameters | 1000 °C, 1 min | N/A | Necessary post-etching treatment to recover NV activity. |
| NV Center Raman Shift | 3115 | cm-1 | Photoluminescence peak frequency used for confirmation. |
| Probe Structure Fabrication | Deep-RIE | N/A | Used on SOI wafer (20/1/455 ”m layers) for Si pillar creation. |
Key Methodologies
Section titled âKey MethodologiesâThe following is a condensed outline of the procedures used to synthesize the diamond particles and construct the scanning probe:
- Substrate Seeding: A 20 x 20 mm silicon substrate was seeded using the electrophoresis method prior to deposition.
- MPCVD Step 1 (Growth): Diamond particles were grown at 700 °C/1000 W/6.7 kPa for 3 hours using Methane (2.5 sccm) and Hydrogen (497.5 sccm).
- MPCVD Step 2 (NV Incorporation): Nitrogen gas (0.5 sccm) was introduced for an additional 0.5 hours to dope the diamond particle surfaces, facilitating NV center formation.
- Si Probe Fabrication: Silicon probes, including cantilever and pillar structures, were fabricated from SOI wafers (20/1/455 ”m thickness profile) using two-step Deep Reactive Ion Etching (Deep-RIE), followed by BHF etching to release the structure.
- Particle Release: The grown diamond particles were released from the Si substrate by etching the underlying silicon using XeFâ gas.
- NV Activation and Cleaning: Released particles were subjected to annealing at 1000 °C for 1 minute. This crucial step removed gas adsorption contamination resulting from the XeFâ etching, which otherwise quenched the NV center photoluminescence.
- Micro-Assembly: Individual NV-active diamond microparticles (identified by 638 nm PL) were selected, picked up using a glass needle, and affixed to the tip of the silicon probe pillar using conductive adhesive glue.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply and engineer the advanced MPCVD diamond materials required to replicate or enhance this research, particularly in the demanding field of quantum sensing and nanoscale MRI.
Applicable Materials & Specifications
Section titled âApplicable Materials & SpecificationsâTo replicate the high-performance magnetic probes described, 6CCVD recommends materials optimized for high-yield NV center generation and integration:
| Component Type | 6CCVD Recommended Material | Rationale & Capability |
|---|---|---|
| Probe Material | Single Crystal Diamond (SCD), Electronic Grade | Provides significantly lower strain and improved coherence times (Tâ) compared to PCD microparticles, crucial for advanced quantum sensing applications. |
| High-Yield NV Precursors | Nâ-Optimized PCD Substrates (up to 125 mm) | For large-area, consistent growth bases. Our MPCVD process is tightly controlled for precise gas flow (Hâ, CHâ, Nâ) to ensure optimized nitrogen incorporation necessary for high-density NV centers. |
| Boron-Doping Potential | Boron-Doped Diamond (BDD) Wafers | Ideal for studies requiring conductive quantum structures or integrated electrodes for electric field control near the NV centers. |
| Thickness Range | SCD/PCD up to 500 ”m | Provides robust material for subsequent Deep-RIE or mechanical milling required to form microstructures or probe supports. |
Customization Potential
Section titled âCustomization PotentialâThe paper utilized highly customized geometric shapes (1.4 ”m particles affixed to a precision Si pillar). 6CCVD provides end-to-end processing support for complex micro-device fabrication:
- Precision Laser Cutting & Dicing: We offer specialized laser services to create diamond micro-disks, micro-wires, or custom facets with precise tolerances, allowing researchers to skip the low-yield particle pick-up stage and use structurally stable diamond tips.
- Custom Dimensions: We supply plates and wafers up to 125 mm (PCD) and offer thickness control from 0.1 ”m up to 500 ”m, meeting the substrate needs for complex lithography and etching processes like the SOI-based RIE employed in this research.
- Integrated Metalization: The assembly relies on conductive glue. 6CCVD offers in-house metal deposition (Au, Pt, Pd, Ti, W, Cu) to create patterned, high-adhesion ohmic contacts directly onto the diamond. This capability replaces less reliable gluing methods and ensures superior electrical and thermal integration of the diamond probe tip.
- Ultra-Low Roughness Polishing: For scanning applications where tip-sample distance is critical, our polishing achieves Ra < 1 nm (SCD) or Ra < 5 nm (Inch-size PCD), minimizing surface defects that can degrade NV center performance.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD engineering team specializes in diamond material science and quantum applications. We can assist with:
- Recipe Optimization: Consultations on precise gas flow ratios (e.g., Nâ/CHâ) and temperature profiles (700 °C) necessary to optimize the NV- formation yield and minimize defect density (such as the graphite peaks detected in the paperâs Step 1 growth).
- Material Selection for Quantum Sensing: Guiding researchers in selecting the optimal diamond platform (PCD vs. SCD, specific dopant concentration) to maximize coherence time (Tâ) and signal-to-noise ratio in similar Nanoscale MRI and quantum sensing projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Magnetic resonance imaging (MRI) is the key technology to investigate anatomy and phyisiology by a non-destructive imaging method. The analysis of molecular structures in nano-scale plays an important role for future nanotechnology. Since the spatial resolution of conventional MRI sytsems is limited to tens of micrometers, the high sensitive magnetic sensor is required for imaging in nanometer spatial resolution. The luminescence of nitrogen vacancy (NV) centers in diamond is sensitive to magnetic field, which applicable to MRI at room temperature through optical detection. Si scanning probes with a diamond particle having the NV centers are developed. Firstly, the diamond particles with the NV centers is deposited on a dummy wafer by microwave plasma chemical vapor deposition (MPCVD) with additional N_2 gas. While a graphite component in the diamond particle is observed by Raman spectroscopy, and the luminescence of the NV centers has been slightly detected. After XeF_2 etching and annealing, diamond particles which own NV centers are picked up and fixed onto the fabricated probe pillar using a glass needle and glue.