Ultrathin boron-doped diamond – surface-wave-plasma synthesis of semi-conductive nanocrystalline boron-doped diamond layers at low temperature
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-01-01 |
| Journal | Materials Advances |
| Authors | P. Ashcheulov, Davydova M, A Taylor, P. Hubík, A. Kovalenko |
| Institutions | Fraunhofer Institute for Applied Solid State Physics |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Ultrathin Semi-Conductive BDD Layers
Section titled “Technical Documentation & Analysis: Ultrathin Semi-Conductive BDD Layers”Executive Summary
Section titled “Executive Summary”This research successfully demonstrates a scalable, low-temperature synthesis route for ultrathin, semi-conductive Boron-Doped Diamond (BDD) layers using Surface-Wave-Plasma (SWP) Microwave Plasma Enhanced CVD (MW-LA-PECVD).
- Low-Temperature Synthesis: BDD layers were fabricated at a substrate temperature of only 500 °C, significantly expanding the range of compatible substrate materials (e.g., glass, quartz, silicon).
- Tunable Electrical Properties: Precise control over gas-phase chemistry (B/C ratio and CO₂ concentration) allowed for tuning of electrical resistivity across five orders of magnitude, from 1.85 Ω cm to 303 kΩ cm, targeting specific semi-conductive applications.
- Ultrathin and Smooth Films: Fabricated layers were consistently ultrathin (approx. 150 nm) and exhibited excellent surface quality, with RMS roughness values between 6 nm and 8 nm, ideal for opto-electronic devices requiring high transparency and minimal light scattering.
- Electrochemical Performance: The resulting Si/BDD electrodes demonstrated a wide electrochemical stability window of 2.5 V to 3.0 V in aqueous electrolytes, comparable to thicker microcrystalline BDD electrodes.
- Scalability Potential: The SWP MW-LA-PECVD technique is inherently scalable, supporting the fabrication of highly homogeneous BDD coatings over large areas (up to 6-inch wafers demonstrated in related work), positioning it as a cost-effective alternative to conventional high-temperature CVD.
Technical Specifications
Section titled “Technical Specifications”Data extracted from the synthesis parameters and material characterization (Table 1 and Table 2).
| Parameter | Value Range | Unit | Context |
|---|---|---|---|
| Substrate Temperature | 500 (±20) | °C | Low-temperature synthesis via plasma heat |
| Layer Thickness | 124 - 167 | nm | Ultrathin nanocrystalline BDD films |
| Electrical Resistivity | 1.85 to 303,500 | Ω cm | Tunable semi-conductive characteristics |
| RMS Surface Roughness | 6 to 8 | nm | Measured via AFM; extremely smooth |
| Growth Rate | < 30 | nm h-1 | Calculated over 6-hour deposition cycle |
| Boron Concentration (Solid) | 6.07 x 1019 to 7.1 x 1020 | at. cm-3 | Measured via GDOES |
| Gas Phase B/C Ratio | 60 to 60,000 | ppm | Primary doping control parameter |
| Gas Phase CO₂ Concentration | 0.1 to 2 | % | Used for quality and resistivity control |
| Electrochemical Stability | 2.5 - 3.0 | V | Wide potential window in aqueous 1 M KCl |
| Metalization Used | Ti (20 nm) / Au (100 nm) | nm | Triangle contacts for electrical characterization |
Key Methodologies
Section titled “Key Methodologies”A concise summary of the experimental recipe used for the SWP MW-LA-PECVD synthesis.
- Reactor System: Custom-built Microwave Plasma Enhanced CVD reactor utilizing Linear Antenna delivery (MW-LA-PECVD).
- Substrate Preparation: Substrates (high-temperature glass, quartz, conductive p-type Si) were cleaned ultrasonically (acetone, IPA, H₂SO₄/H₂O₂ mixture). Si substrates received an additional HF acid treatment to remove the native SiO₂ layer.
- Nucleation: Substrates were seeded using spin coating with a nanodiamond dispersion (NanoAmando, 0.2 g L-1 in water).
- Gas Chemistry: H₂ (94-96%) and CH₄ (4%) were used as the primary precursors. B₂H₆ (7500 ppm in H₂) was the boron precursor, and CO₂ (0.1% to 2%) was added for quality control and resistivity tuning.
- Process Parameters:
- Microwave Power: 2 x 3 kW.
- Process Pressure: 0.25 mbar.
- Substrate Holder Configuration: Unassisted (relying solely on plasma heat).
- Growth Duration: 6 hours for all samples to ensure comparative analysis.
- Characterization Techniques: GDOES (Boron concentration), SEM (Thickness, Morphology, Grain Size), AFM (Roughness), Raman Spectroscopy (Quality, sp³/sp² ratio), and differential van der Pauw (vdP) method (Resistivity).
- Electrode Fabrication: Ti (20 nm) / Au (100 nm) triangle contacts were evaporated onto BDD/glass samples for electrical measurements.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is uniquely positioned to support the replication and industrial scaling of this low-temperature BDD synthesis for advanced electrochemical and opto-electronic applications.
| Research Requirement | 6CCVD Solution & Capability | Value Proposition |
|---|---|---|
| Material: Nanocrystalline BDD (NCD) | Polycrystalline Diamond (PCD) / Boron-Doped Diamond (BDD). We offer NCD films with precise control over grain size and doping levels. | Guaranteed material quality to replicate the semi-conductive characteristics (1.85 Ω cm to 303 kΩ cm) required for sensing and electroanalysis. |
| Thickness: Ultrathin (124-167 nm) | SCD/PCD/BDD Thickness Control: 0.1 µm (100 nm) to 500 µm. | We provide precise, custom-grown ultrathin films, ensuring the mechanical flexibility and optical transparency critical for these applications. |
| Scalability: Wafer-size deposition | Large-Area PCD Wafers: Up to 125 mm diameter. | Transition research from 10x10 mm² coupons to production-ready, inch-size wafers, leveraging the scalability of the SWP method. |
| Surface Quality: RMS Roughness 6-8 nm | Advanced Polishing Services: Ra < 5 nm on inch-size PCD. | Achieve superior surface smoothness necessary for minimizing light scattering in opto-electronic devices and ensuring uniform coating adhesion. |
| Electrode Integration: Ti/Au contacts | In-House Custom Metalization: Au, Pt, Pd, Ti, W, Cu. | Rapid prototyping and integration of complex electrode patterns directly onto BDD films, eliminating external processing steps and ensuring optimal contact resistance. |
| Engineering Support: Low-T CVD expertise | In-House PhD Material Science Team. | 6CCVD’s experts can assist with material selection and recipe optimization (e.g., B/C ratio, CO₂ tuning) for similar low-temperature electrochemical electrode projects. |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Ultrathin boron-doped diamond layers, synthesized at 500 °C, provide a cost-effective, energy-efficient material with moderate semi-conductive properties for advanced functional uses.