Diamond anvil cell with boron-doped diamond heater for high-pressure synthesis and in situ transport measurements

At a Glance

Metadata	Details
Publication Date	2021-08-02
Journal	Applied Physics Letters
Authors	Ryo Matsumoto, Sayaka Yamamoto, Shintaro Adachi, Takeshi Sakai, Tetsuo Irifune
Institutions	University of Tsukuba, Kyoto University of Advanced Science
Citations	10
Analysis	Full AI Review Included

Technical Documentation & Analysis: Boron-Doped Diamond DAC Components

This analysis focuses on the fabrication and application of Boron-Doped Diamond (BDD) components for high-pressure, high-temperature (HPHT) Diamond Anvil Cells (DACs), a core application area where 6CCVD’s advanced MPCVD capabilities provide critical material solutions.

Executive Summary

The research successfully developed a highly stable and reusable Diamond Anvil Cell (DAC) integrating in-situ electrical transport measurement capabilities, resistive heating, and thermometry, all fabricated from Boron-Doped Diamond (BDD) epitaxial films.

Integrated Functionality: The DAC incorporates BDD-based probes, heaters, and thermometers directly onto the diamond anvil surface, enabling simultaneous control and measurement of temperature and pressure.
Extreme Conditions Achieved: The system demonstrated stable operation under high pressure (tested up to 3 GPa) and high temperature (sample space exceeding 1000 K).
Material Stability: BDD components exhibited exceptional chemical and mechanical stability, allowing for repeated use and acid cleaning (HNO₃/H₂SO₄) without degradation under HPHT conditions.
Fabrication Expertise: Components were fabricated using a combination of electron beam lithography and Microwave Plasma-Assisted Chemical Vapor Deposition (MPCVD), confirming the viability of advanced diamond processing for complex instrumentation.
Scientific Breakthrough: The developed DAC was successfully used for high-pressure annealing of La(O,F)BiS₂ single crystals, achieving a quenched high-T_c phase (3 K to 8 K), and synthesizing EuFBiS₂ superconductors.
Tunable Properties: The study highlights the necessity of tuning boron concentration (N_B) in the BDD film to control electrical behavior, specifically preventing resistance-temperature (R-T) curve saturation at high temperatures (>800 K) for accurate thermometry.

Technical Specifications

Parameter	Value	Unit	Context
Maximum Sample Temperature	>1000	K	Achieved in the sample chamber during heating tests.
Maximum Test Pressure	3	GPa	Pressure maintained during resistive heating experiments.
BDD Thermometer Saturation	~800	K	Temperature limit for heavily doped (metallic) BDD calibration.
La(O,F)BiS₂ Annealing Temp.	1100	K	Maximum temperature reached during annealing test (0.7 GPa).
La(O,F)BiS₂ T_c Enhancement	3 to 8	K	T_c enhanced and quenched to ambient pressure.
EuFBiS₂ Synthesis Temp./Pressure	900 K / 3.1 GPa	K / GPa	Conditions held for 3 minutes during synthesis.
EuFBiS₂ Critical Field (B_c2)	Up to 7	T	Measured suppression of superconductivity post-synthesis.
BDD Fabrication Method	MPCVD	N/A	Microwave Plasma-Assisted Chemical Vapor Deposition.
Anvil Material Types Used	Single-Crystalline, Nano-Polycrystalline	N/A	Used as substrates for BDD film growth.

Key Methodologies

The successful integration of functional BDD components required precise control over material growth and patterning, utilizing techniques central to 6CCVD’s expertise:

BDD Film Growth: Boron-doped diamond epitaxial films were grown homoepitaxially onto the diamond anvil surface using Microwave Plasma-Assisted Chemical Vapor Deposition (MPCVD).
Component Patterning: Electron beam lithography was employed to define the high-resolution patterns for the four-probe measurement electrodes, resistive heater, and resistive thermometer.
Boron Concentration Tuning: Boron concentration (N_B) was precisely controlled to achieve specific electrical properties:
- Heavily doped (metallic) BDD for high conductivity (heater/probes).
- Lightly doped (insulating) BDD to prevent R-T curve saturation above 800 K, ensuring accurate high-temperature thermometry.
Calibration Environment: The BDD thermometer was calibrated by measuring its Resistance-Temperature (R-T) relationship in a tube furnace under N₂ gas flow to prevent oxidation of the diamond surface.
HPHT Configuration: The DAC utilized a SUS316 gasket, cubic boron nitride (cBN) pressure medium, and various backup plates (Si₃N₄, Al₂Si₄O₁₀(OH)₂, ZrO₂) selected based on thermal conductivity and mechanical hardness.
In-Situ Measurement: Electrical transport properties (resistance) were monitored using a standard four-probe method during simultaneous compression and resistive heating.
Post-Experiment Cleaning: The BDD components were successfully cleaned and regenerated using a mixture of HNO₃ and H₂SO₄, confirming the reusability of the diamond-based instrumentation.

6CCVD Solutions & Capabilities

The research demonstrates a critical need for high-quality, customized Boron-Doped Diamond (BDD) substrates and advanced fabrication services—precisely the core offering of 6CCVD. We are uniquely positioned to supply the materials required to replicate, scale, and extend this HPHT research.

Applicable Materials

To achieve the precise electrical and thermal performance required for integrated DAC components, 6CCVD recommends the following materials:

Component Requirement	6CCVD Material Solution	Key Specification Match
Anvil Substrate	Optical Grade SCD	High purity, low birefringence SCD substrates (up to 500 µm thickness) for maximum optical transparency (X-ray/laser analysis).
Heater/Probes	Heavy Boron Doped SCD (Metallic)	Precisely controlled N_B for metallic conductivity and high thermal stability required for resistive heating and low-resistance probes.
Thermometer	Light Boron Doped SCD (Insulating/Semi-Metallic)	Tunable N_B to prevent R-T saturation above 800 K, ensuring accurate temperature measurement up to 1200 K.
Large-Scale Anvils	High-Quality PCD	Polycrystalline diamond plates up to 125mm in diameter, suitable for nano-polycrystalline anvils mentioned in the study [21].

Customization Potential

6CCVD’s in-house fabrication and processing capabilities directly address the complex engineering challenges presented by integrated DAC design:

Custom Dimensions and Thickness: We supply SCD and PCD plates/wafers in custom dimensions, ensuring perfect fit for various DAC geometries (e.g., culet-type anvils). SCD thickness is available from 0.1 µm up to 500 µm.
Advanced Patterning & Lithography: We offer high-resolution patterning services necessary to define the micron-scale probes, heaters, and thermometers via electron beam lithography, replicating the methodology used in this research.
Custom Metalization: While the BDD film itself acts as the electrode/heater, external contacts often require metalization. 6CCVD provides internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for robust electrical connections and bonding pads, crucial for high-current applications.
Surface Finish: Our SCD substrates feature ultra-low roughness (Ra < 1 nm), minimizing defects that could compromise the integrity of the thin BDD epitaxial film or the lithographic patterns under extreme pressure.

Engineering Support

The successful synthesis of high-T_c superconductors like La(O,F)BiS₂ and EuFBiS₂ under HPHT conditions relies entirely on the stability and precision of the diamond components. 6CCVD’s in-house PhD team specializes in the physics and chemistry of MPCVD diamond growth. We offer consultation services to assist researchers in:

Optimizing Boron concentration for specific R-T curve profiles (e.g., avoiding saturation for high-temperature thermometry).
Selecting the optimal diamond substrate (SCD vs. PCD) based on required optical transparency and mechanical strength for similar HPHT Superconductor Synthesis projects.
Designing robust metalization schemes for high-current resistive heating applications.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Temperature and pressure are essential parameters in the synthesis, evaluation, and application of functional materials. This study proposes the addition of a heating function to a high-pressure diamond anvil cell (DAC) with in situ measurement probes. The proposed DAC allows for simultaneous control of temperature and pressure within the sample space and can be used to synthesize functional materials under extreme conditions. The various components, namely, the heater, thermometer, and measurement probes, were fabricated with a boron-doped diamond epitaxial film and could be repeatedly used. The developed DAC was used to conduct the high-pressure annealing of a La(O,F)BiS2 single crystal and the high-pressure synthesis of EuFBiS2 superconductors. The proposed technique shows promise for further exploration of superconductors to broaden the research field.

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0059705

References

2004 - Superconducting materials for large scale applications [Crossref]
2004 - Development of new types of DI-BSCCO wire
2015 - Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system [Crossref]
2016 - Crystal structure of the superconducting phase of sulfur hydride [Crossref]
2019 - Superconductivity of pure H3S synthesized from elemental sulfur and hydrogen [Crossref]
2019 - Superconductivity at 250 K in lanthanum hydride under high pressures [Crossref]
2019 - Evidence for superconductivity above 260 K in lanthanum superhydride at megabar pressures [Crossref]
2020 - Superconductivity at 161 K in thorium hydride ThH10: Synthesis and properties [Crossref]