Electrical transport measurements for superconducting sulfur hydrides using boron-doped diamond electrodes on beveled diamond anvil
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-10-02 |
| Journal | Superconductor Science and Technology |
| Authors | Ryo Matsumoto, Mari Einaga, Shintaro Adachi, Sayaka Yamamoto, Tetsuo Irifune |
| Institutions | Osaka University, National Institute for Materials Science |
| Citations | 12 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Integrated BDD Electrodes for Ultra-High Pressure Superconductivity
Section titled âTechnical Documentation & Analysis: Integrated BDD Electrodes for Ultra-High Pressure Superconductivityâ6CCVD specializes in providing high-quality, custom Microwave Plasma Chemical Vapor Deposition (MPCVD) diamond materials essential for extreme environment research, such as Diamond Anvil Cell (DAC) applications. This analysis reviews the fabrication and performance of integrated Boron-Doped Diamond (BDD) electrodes used for in-situ electrical transport measurements of high-Tc superconductors.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Successful fabrication of highly stable, integrated Boron-Doped Diamond (BDD) micro-electrodes and Undoped Diamond (UDD) insulating layers directly onto beveled diamond anvils.
- Methodology: The electrodes were fabricated using a combination of MPCVD epitaxial growth and Electron Beam Lithography (EBL) techniques, ensuring components are grown directly from the diamond anvil surface.
- Extreme Conditions: The developed DAC configuration enabled stable electrical transport measurements up to an extreme pressure of 192 GPa.
- Application: Demonstrated in-situ synthesis and characterization of superconducting sulfur hydrides (H2S $\rightarrow$ H3S/HS2$), known for high transition temperatures.
- Superconductivity Observed: A clear two-step superconducting transition was observed, characterized by a higher Tc1 (~25 K) phase and a lower Tc2 (< 15 K) phase, both exhibiting zero resistance.
- Material Stability: Epitaxial growth provides a significant advantage over traditional inserted electrodes, offering enhanced stability and reusability under severe pressure cycling and chemical reaction conditions.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper, highlighting the extreme conditions and material properties achieved.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Pressure Achieved | 192 | GPa | Electrical transport measurements |
| Higher Superconducting Tc1 | ~25 | K | Observed under 120-154 GPa |
| Lower Superconducting Tc2 | < 15 | K | Observed under 120-154 GPa |
| Extrapolated Upper Critical Field Hc2(0) (Tc1) | 53.0 | T | At 154 GPa |
| Extrapolated Upper Critical Field Hc2(0) (Tc2) | 28.2 | T | At 154 GPa |
| Coherence Length Ο(0) (Tc1) | 2.5 | nm | Ginzburg-Landau calculation |
| BDD Growth Microwave Power | 500 | W | H2-induced MPCVD |
| UDD Growth Microwave Power | 350 | W | MPCVD insulating layer |
| BDD Boron/Carbon Ratio | 2500 | ppm | Tuned using C3H9B gas |
| BDD Growth Pressure | 70 | Torr | Total pressure |
| UDD Growth Pressure | 35 | Torr | Total pressure |
| Sample Space Dimensions | 15 x 20 | ”m | Surrounded by UDD insulation |
| DAC Anvil Diameter (First/Second) | 300 / 100 | ”m | Beveled culet dimensions |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication of the integrated BDD micro-electrodes and UDD insulating layer relies on precise MPCVD control and advanced lithography:
- Lithography and Patterning: Electrode shape defined on the beveled anvil culet surface using Electron Beam Lithography (EBL) combined with a nanofabrication system.
- Metal Mask Deposition: A Ti/Au thin film metal mask was deposited onto the resist via a lift-off process.
- Adhesion Layer Formation: The assembly was annealed at 450°C for 1 hour under Ar gas-flow to form a stable TiC intermediate layer, enhancing adhesion between the diamond and the metal mask.
- BDD Micro-electrode Epitaxial Growth: Selective epitaxial BDD was grown onto the uncovered diamond surface using H2-induced MPCVD. Growth parameters included 70 Torr total pressure, 300 sccm total gas flow, and 500 W microwave power, utilizing CH4 and C3H9B (2500 ppm B/C ratio).
- Mask Removal and Cleaning: Wet etching (HNO3 and H2SO4$ at 400°C for 30 min) was used to remove the Ti/Au mask and any graphite impurities.
- UDD Insulation Layer Growth: An undoped diamond (UDD) layer was deposited around the BDD electrodes using similar MPCVD processes (35 Torr, 400 sccm, 350 W) to provide electrical insulation for the 15 ”m x 20 ”m sample space.
- In-Situ Measurement: Electrical transport was measured using a standard four-probe method under low-temperature, high-pressure conditions (up to 192 GPa).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and extension of this high-pressure research depend entirely on the quality and customization of the MPCVD diamond materials and associated micro-fabrication services. 6CCVD is uniquely positioned to supply the necessary components for next-generation DAC experiments.
| Requirement from Paper | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| BDD Micro-electrode Material | Heavy Boron-Doped SCD (SCD-BDD) or PCD-BDD Wafers. | We specialize in high-conductivity BDD growth via MPCVD, ensuring the low resistivity and high stability required for reliable four-probe measurements under extreme pressure. |
| Anvil Substrate & Insulation | High Purity Optical Grade SCD (Substrates up to 10mm thick). | Our SCD material provides the necessary mechanical strength and optical transparency for DAC anvils, while our UDD epitaxial growth services ensure superior dielectric insulation (as required for the 15 ”m sample space). |
| Custom Dimensions & Geometry | Custom Dimensions: Plates/wafers up to 125mm (PCD). Custom thickness (SCD: 0.1”m - 500”m). | We can supply the base diamond material in the precise beveled culet dimensions (e.g., 300 ”m or 100 ”m) required for high-pressure cell assembly, minimizing preparation time for researchers. |
| Micro-Patterning & Lithography | Advanced Laser Cutting and EBL/FIB Preparation Support. | We can assist in preparing the complex micro-geometry of the anvil culet, ensuring the surface quality (Ra < 1nm for SCD) necessary for subsequent high-resolution lithography and epitaxial growth. |
| Electrode Metalization | Internal Metalization Capability: Ti, Au, Pt, Pd, W, Cu. | We offer the exact Ti/Au metal stack used in this study, including the ability to perform the high-temperature annealing step (450°C) to form the critical TiC adhesion layer, guaranteeing robust electrical contacts. |
| Global Logistics | Global Shipping (DDU default, DDP available). | We ensure rapid and secure delivery of sensitive, custom-fabricated diamond components worldwide. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists can provide expert consultation on optimizing diamond material selection (e.g., doping concentration, crystal orientation, and surface termination) for similar High-Pressure Superconductivity or DAC Transport Measurement projects. We ensure the diamond properties meet the stringent requirements of multi-megabar physics experiments.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract A diamond anvil cell (DAC) has become an effective tool for investigating physical phenomena that occur at extremely high pressure, such as high-transition temperature superconductivity. Electrical transport measurements, which are used to characterize one of the most important properties of superconducting materials, are difficult to perform using conventional DACs. The available sample space in conventional DACs is very small and there is an added risk of electrode deformation under extreme operating conditions. To overcome these limitations, we herein report the fabrication of a boron-doped diamond microelectrode and undoped diamond insulation on a beveled culet surface of a diamond anvil. Using the newly developed DAC, we have performed in-situ electrical transport measurements on sulfur hydride H 2 S, which is a well-known precursor of the pressure-induced, high-transition temperature superconducting sulfur hydride, H 3 S. These measurements conducted under high pressures up to 192 GPa, indicated the presence of a multi-step superconducting transition, which we have attributed to elemental sulfur and possibly HS 2 .