Note - Novel diamond anvil cell for electrical measurements using boron-doped metallic diamond electrodes
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-07-01 |
| Journal | Review of Scientific Instruments |
| Authors | R. Matsumoto, Y. Sasama, Fujioka M, T Irifune, M. Tanaka |
| Institutions | University of Tsukuba, National Institute for Materials Science |
| Citations | 46 |
| Analysis | Full AI Review Included |
Novel Diamond Anvil Cell for Electrical Measurements using Boron-doped Metallic Diamond Electrodes
Section titled âNovel Diamond Anvil Cell for Electrical Measurements using Boron-doped Metallic Diamond ElectrodesâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the key technical advancements detailed in the paper regarding the development of a novel Diamond Anvil Cell (DAC) electrode system, highlighting the crucial role of specialized MPCVD Boron-Doped Diamond (BDD) and nano-polycrystalline diamond (NPD) substrates.
- Core Achievement: Successful development of a DAC system using metallic boron-doped diamond (BDD) thin films as robust, reusable electrodes for high-pressure electrical transport measurements.
- Superior Performance: The BDD electrodes demonstrated zero degradation and high mechanical stability after repeated compression cycles, a significant improvement over traditional metal foil electrodes.
- Ultra-High Pressure: The system achieved a maximum confirmed pressure of 31.1 GPa using a 0.4 mm culet NPD anvil, validating its suitability for geophysics and material science research under extreme conditions.
- Material Recipe: BDD films were fabricated via Microwave Plasma-Assisted Chemical Vapor Deposition (MPCVD), requiring a minimum boron concentration exceeding 3 x 1020 cm-3 to ensure metallic conductivity.
- Fabrication Method: The microscale electrode structures were patterned via a combination of Electron Beam Lithography (EBL) and MPCVD selective deposition, requiring precise material control and micro-fabrication expertise.
- Validation: Electrical transport measurements on lead (Pb) confirmed the metallic behavior and superconducting transition ($T_c$) up to 8 GPa, matching previously reported values.
Technical Specifications
Section titled âTechnical SpecificationsâHard parameters extracted from the experimental data concerning the DAC setup and material properties.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Pressure Achieved | 31.1 | GPa | Highest pressure reached during stroke testing (0.4 mm culet). |
| Operational Pressure Range (Pb $T_c$ Test) | 0 to 8 | GPa | Range used for verifying electrical transport capabilities. |
| BDD Electrode Film Thickness | 100 | nm | Thickness achieved via MPCVD deposition (2.5 minute process). |
| Minimum Boron Concentration for Metallicity | > 3 x 1020 | cm-3 | Required concentration threshold for BDD to exhibit metallic properties. |
| High-Pressure Anvil Culet Size | 0.4 | mm | Culet dimension used to achieve pressures > 30 GPa. |
| Gasket Material / Thickness | Stainless steel / 200 | ”m | Used to contain the sample and pressure medium. |
| Insulation Material | Cubic Boron Nitride (cBN) | Powder | Used for electrical isolation between the electrode and gasket. |
| Pb Superconducting Transition $T_c$ (Ambient) | 7.2 | K | Baseline measurement of the test sample at 0 GPa. |
| Pressure Dependence of $T_c$ (Pb) | -0.357 | K/GPa | Estimated value showing rate of change of $T_c$ with applied pressure. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment successfully combined advanced lithography with MPCVD diamond growth to produce the specialized electrode assembly.
Fabrication Sequence for BDD Electrodes on NPD Anvils
Section titled âFabrication Sequence for BDD Electrodes on NPD Anvilsâ- Substrate Preparation: Nano-Polycrystalline Diamond (NPD) anvils were selected for their high mechanical hardness and stability under extreme pressure.
- Patterning Design: The four-terminal electrode structure was designed using Electron Beam Lithography (EBL).
- Mask Deposition: A Ti/Pt metal mask was deposited onto the patterned resist layer.
- Lift-Off: Excess metal mask material was removed via a lift-off process, leaving behind a patterned mask structure on the NPD surface.
- Selective MPCVD Growth: Heavily Boron-Doped Diamond (BDD) thin films were deposited selectively onto the exposed regions of the NPD anvil using the Microwave Plasma-Assisted Chemical Vapor Deposition (MPCVD) method.
- Note: Deposition parameters were controlled to achieve the required 100 nm thickness and ensuring the boron concentration exceeded $3 \times 10^{20}$ cm-3.
- Assembly and Testing: The fabricated NPD anvil with BDD electrodes was assembled into the DAC with a stainless steel gasket and cBN powder used for electrical insulation and pressure transmission.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to support the replication and scaling of this research, offering the critical materials and precision engineering services required for advanced high-pressure sensing and electrical applications.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the ultra-stable, conductive electrodes used in this research, 6CCVD recommends heavily doped BDD films on robust PCD substrates:
- Heavy Boron-Doped Diamond (BDD): Available as high-quality MPCVD thin films (0.1 ”m to 500 ”m thick) or thick substrates. We guarantee the control necessary to achieve and sustain the metallic doping concentrations (> 3 x 1020 cm-3) required for superconducting/metallic conductivity and low-noise transport measurements.
- High-Durability Polycrystalline Diamond (PCD): We offer NPD/PCD substrates (up to 125mm diameter) engineered for superior mechanical strength, ideal for acting as the anvil base in high-pressure systems where durability is paramount.
- Optical Grade SCD: For configurations requiring transparent diamond anvils, 6CCVD can supply Single Crystal Diamond (SCD) with ultra-low nitrogen content and superior optical clarity for advanced laser diagnostics (e.g., ruby fluorescence measurements).
Customization Potential
Section titled âCustomization PotentialâThe experiment relies heavily on precise micro-fabrication and specific material dimensions, all of which fall within 6CCVDâs core engineering capabilities:
| Research Requirement | 6CCVD Engineering Service |
|---|---|
| Thin Film Deposition Control (Precise 100 nm BDD film) | MPCVD Thickness Precision: We provide SCD and PCD/BDD films with guaranteed thickness tolerances, essential for reproducible micro-scale electrode manufacturing. |
| Anvil Custom Geometry (Specific culet sizes, e.g., 0.4 mm) | Precision Laser Cutting & Machining: 6CCVD offers in-house laser cutting services to prepare PCD/SCD substrates to custom culet sizes, reducing manufacturing steps for the end researcher. |
| Contact Layer Deposition (Requirement for Ti/Pt metal mask) | Internal Metalization Capability: We offer custom Ti/Pt (as used in the paper), Au, Pd, W, and Cu metal stacks deposited directly onto the BDD surface, ready for subsequent lithography or wire bonding, streamlining electrode fabrication. |
| Surface Finish (Optimizing lithography process) | Ultra-Low Roughness Polishing: We achieve roughness Ra < 5 nm for inch-size PCD and Ra < 1 nm for SCD. This extreme smoothness is vital for minimizing scattering and ensuring high-fidelity lithographic patterning. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists specializes in optimizing diamond material parametersâsuch as doping, defect density, and mechanical propertiesâfor specific engineering challenges.
We provide comprehensive support for researchers working on High-Pressure Electrical Transport projects and related applications, including:
- Selection of the optimal PCD/NPD substrate grade to maximize mechanical stability and handle GPa pressures.
- Tailoring BDD doping profiles to achieve specific target resistivity or critical temperatures ($T_c$).
- Designing robust metalization schemes compatible with cryogenic and high-pressure environments.
For custom specifications or material consultation regarding high-pressure BDD electrodes, visit 6ccvd.com or contact our engineering team directly. We ship materials globally (DDU default, DDP available).
View Original Abstract
A novel diamond anvil cell suitable for electrical transport measurements under high pressure has been developed. A boron-doped metallic diamond film was deposited as an electrode on a nano-polycrystalline diamond anvil using a microwave plasma-assisted chemical vapor deposition technique combined with electron beam lithography. The maximum pressure that can be achieved by this assembly is above 30 GPa. We report electrical transport measurements of Pb up to 8 GPa. The boron-doped metallic diamond electrodes showed no signs of degradation after repeated compression.