Diamond with Sp2-Sp3 composite phase for thermometry at Millikelvin temperatures
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-05-08 |
| Journal | Nature Communications |
| Authors | Jianan Yin, Yan Yang, Mulin Miao, Jiayin Tang, Jiali Jiang |
| Institutions | City University of Hong Kong, Shenzhen Research Institute, China Resources (China) |
| Citations | 9 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThe research introduces a novel diamond material, the sp2-sp3 Composite Phase Diamond (CPD), specifically engineered for ultra-low temperature (cryogenic) thermometry.
- Ultra-Low Temperature Limit: The CPD material achieves a theoretical temperature measurement limit of 1 mK, significantly advancing the capability of solid-state thermometers beyond the traditional 20 mK limit.
- High Accuracy and Fit: The resistance-temperature (R-T) curve exhibits a Negative Temperature Coefficient (NTC) and demonstrates an exceptional goodness of fit (R2 = 0.99999) across a broad range (3 K to 400 K).
- Magnetic Field Insensitivity: CPD shows remarkably low sensitivity to strong magnetic fields, with a resistance shift rate of only -3% at 2 K under a 9 T field, making it ideal for use in NMR and quantum systems.
- Enhanced Thermal Stability: The unique sp2/sp3 composite structure unexpectedly boosts high-temperature oxidation resistance, raising the onset oxidation temperature (Tonset) to 1163 K (compared to 948 K for the original diamond).
- High Conductivity: The material maintains a high room-temperature electrical conductivity (1.2 S·cm-1), minimizing self-heating effects crucial for accurate low-temperature sensing.
- Scalable Fabrication: The synthesis method is straightforward and cost-efficient, allowing for fabrication into micro-scale probes (down to 1 ”m) via Focused Ion Beam (FIB) and complex structures via 3D printing.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Lowest Measurement Limit | 1 | mK | Theoretical detection limit |
| Temperature Resolution | 1 | mK | Achieved at temperatures less than 10 K |
| R-T Curve Fit Goodness (3-400 K) | 0.99999 | R2 | Fitted using Expdec3 function |
| R-T Curve Fit Goodness (<1 K) | 0.99775 | R2 | Fitted using Expdec3 function |
| Room Temperature Conductivity | 1.2 | S·cm-1 | Exceptional conductivity |
| Magnetic Field Sensitivity | -3 | % | Resistance shift rate at 2 K under 9 T field |
| Onset Oxidation Temperature (CPD) | 1163 | K | Measured in air (enhanced stability) |
| Thermal Response Time (0-90% step) | 2.04 | s | Response time when plunged into liquid nitrogen |
| Band Gap (UV-Vis DRS) | 1.87 | eV | Lower than standard diamond (5.47 eV) |
| Ionization Energy (UPS) | 7.84 | eV | Lower than standard diamond (81 eV) |
| Minimum Probe Diameter | 1 | ”m | Fabricated using Focused Ion Beam (FIB) |
Key Methodologies
Section titled âKey MethodologiesâThe sp2-sp3 Composite Phase Diamond (CPD) was synthesized via a straightforward heat-treatment process of synthetic diamond powder under atmospheric pressure.
- Precursor Mixing: Commercial synthetic Type 1b diamond powder (80 ”m particles) was fully mixed with an acrylic acid ammonium salt polymer, acrylamide, and various photoinitiators (including N, Nâ-Methylenebisacrylamide and 2-hydroxy-2-methylpropiophenone) in water.
- 3D Printing: The resulting slurry was printed using a Direct Ink Writing (DIW) 3D printer, utilizing a crosshatch pattern to achieve a 0.4 mm line width.
- Curing and Drying: Preliminary curing was performed using a 365 nm ultraviolet lamp, followed by drying the sample at 80 °C for 4 hours.
- Sintering (Heat Treatment): The dried sample was sintered in a tube furnace (BTF-1700C) at a temperature of 1250 °C.
- Atmosphere and Duration: Sintering was conducted under atmospheric pressure in an Argon (Ar) atmosphere for a standard duration of 1800 minutes (30 hours).
- Cleaning: The final CPD samples were ultrasonically cleaned in anhydrous ethanol.
Commercial Applications
Section titled âCommercial ApplicationsâThe unique combination of ultra-low temperature sensing capability, high stability, and magnetic field insensitivity positions CPD as a critical material for next-generation precision instruments.
- Quantum Technology:
- Quantum Computing/Simulation: Essential for monitoring and stabilizing the temperature of superconducting or trapped-ion qubits, which require operation near absolute zero (mK range).
- Quantum Sensing: Used in advanced sensors where localized, high-resolution temperature measurement is needed in the presence of strong magnetic fields.
- Cryogenic Engineering:
- Dilution Refrigerators and Cryostats: Direct replacement or enhancement for traditional cryogenic thermometers (like RuO2 or Germanium) that lose sensitivity or fail below 20 mK.
- Magnetic Resonance (NMR/MRI): The low magnetoresistance simplifies calibration and improves accuracy when measuring temperatures within high-field superconducting magnets.
- Precision Measurement and Micro-Devices:
- Micro-Thermometry: Fabrication into 1 ”m diameter probes allows for highly localized temperature mapping in micro-electronic circuits and medical devices operating at cryogenic temperatures.
- Extreme Environment Applications:
- Space Technology: The exceptional thermal stability (Tonset = 1163 K) and mechanical robustness of diamond make CPD suitable for sensors that must survive extreme temperature fluctuations during storage or operation.