Effect of Boron Doping on Diamond Film and Electrochemical Properties of BDD According to Thickness and Morphology
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-03-30 |
| Journal | Coatings |
| Authors | Chang Song, DaeâSeung Cho, JaeâMyung Lee, Pung Keun Song |
| Institutions | Pusan National University |
| Citations | 19 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research details the successful, low-cost manufacturing of high-performance Boron-Doped Diamond (BDD) films on titanium (Ti) substrates using Hot-Filament Chemical Vapor Deposition (HFCVD).
- Cost Reduction & Source Material: Acetone and trimethyl borate (TMB) were utilized as low-cost carbon and boron sources, injected via a bubbling system, significantly reducing manufacturing expenses compared to conventional methods.
- Substrate Stabilization: A critical challengeâTi substrate bending due to thermal mismatch during high-temperature depositionâwas solved by applying a 3 ”m columnar Niobium (Nb) interlayer via HiPIMS sputtering, acting as a thermal buffer.
- Process Efficiency: The BDD film exhibited a highly stable average deposition rate of 100 nm/h, confirmed across both 12-hour (1.22 ”m) and 60-hour (5.91 ”m) runs.
- Doping Level: Boron was successfully incorporated into the diamond lattice at a calculated concentration of 7902 ppm (B/C ratio = 0.007902), confirmed by characteristic shifts in the Raman spectra.
- Electrochemical Superiority: The deposited BDD films showed an increased potential window compared to commercial reference BDD, demonstrating improved electrochemical properties.
- Quality Control Insight: Improved electrochemical performance was directly linked to controlling the deposition temperature to prevent amorphous carbonization, confirming that film quality is more critical than thickness or density.
- Performance Driver: Electrochemical activation and catalytic ability were found to be dependent solely on the intrinsic properties of the exposed BDD surface particles, not the overall film thickness.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| BDD Deposition Rate (Average) | 100 | nm/h | HFCVD process stability |
| Boron Doping Concentration | 7902 | ppm | Calculated B/C ratio (0.007902) |
| HFCVD Filament Power | 16 | kW | Total power for 12 Tantalum filaments |
| HFCVD Working Pressure | 4000 | Pa | Deposition environment |
| Acetone Flux (Carbon Source) | 90 | sccm | HFCVD input |
| Trimethyl Borate (TMB) Flux (Boron Source) | 6 | sccm | HFCVD input |
| Hydrogen Flux | 400 | sccm | Carrier gas |
| Nb Interlayer Thickness | 3 | ”m | Columnar structure deposited via HiPIMS |
| Nb Interlayer Deposition Temp. | 100 | °C | HiPIMS process temperature |
| Ti Substrate Thickness | 1 | mm | Substrate used for electrode analysis |
| Diamond Film Thickness (12 h) | 1.22 | ”m | Measured via FE-SEM |
| Diamond Film Thickness (60 h) | 5.91 | ”m | Measured via FE-SEM |
| Diamond Raman Peak Shift (Doped) | 1210 & 490 | cm-1 | Characteristic broad peaks indicating successful boron doping |
| CV Measurement Scan Rate | 20 | mV/s | Electrochemical testing condition |
Key Methodologies
Section titled âKey MethodologiesâThe BDD films were fabricated using a two-step process involving Physical Vapor Deposition (PVD) sputtering for the interlayer and Hot-Filament Chemical Vapor Deposition (HFCVD) for the diamond film.
-
Substrate Preparation and Interlayer (HiPIMS):
- Titanium (Ti) plates were selected as the low-cost substrate.
- To manage the severe thermal expansion mismatch between Ti (8.6 ”m/(mK)) and diamond (1.2 ”m/(mK)), a Niobium (Nb) interlayer was deposited.
- High-Power Impulse Magnetron Sputtering (HiPIMS) was used to deposit a 3 ”m thick Nb layer with a columnar structure at 100 °C for 1 hour, successfully preventing substrate bending and diamond delamination.
-
BDD Film Deposition (HFCVD):
- The HFCVD system employed 12 tantalum filaments operating at 16 kW.
- Low-cost liquid precursors, Acetone (C3H6O6) and Trimethyl Borate (TMB, C3H9O3B), were introduced into the chamber via a bubbling system.
- Gas flow rates were precisely controlled: Acetone (90 sccm), TMB (6 sccm), and Hydrogen (400 sccm).
- Deposition was performed at a working pressure of 4000 Pa.
- Deposition times of 12 hours and 60 hours were used to study the effect of thickness on electrochemical properties.
-
Doping Calculation:
- The boron doping ratio was calculated using the Antoine equation based on the vapor pressures of Acetone (70.2047 torr) and TMB (25.5690 torr) at 0 °C, yielding a B/C ratio of 0.007902 (7902 ppm).
-
Characterization and Testing:
- Structural Analysis: FE-SEM confirmed morphology and measured film thickness (100 nm/h average rate).
- Quality Confirmation: Raman spectroscopy verified successful boron doping (broad peaks) and confirmed the absence of significant amorphous carbonization in the optimized films.
- Phase Analysis: XRD confirmed the presence of diamond and niobium carbide (formed by carbonization of the Nb interlayer).
- Electrochemical Testing: Cyclic Voltammetry (CV) was used to measure the potential window (using 0.5 M Na2SO4) and catalytic activity (using 50 mM K3Fe(CN)6/K4Fe(CN)6 solution).
Commercial Applications
Section titled âCommercial ApplicationsâThe development of cost-effective, high-performance BDD films on robust Ti substrates directly targets several high-growth industrial sectors:
- Advanced Water and Wastewater Treatment:
- BDD electrodes are superior to conventional IrO2 electrodes due to their ability to generate powerful hydroxyl radicals, enabling highly effective electrochemical oxidation of persistent organic pollutants.
- Applications include the treatment of industrial effluents, including those contaminated with organotin compounds, fluorotelomers, and poorly biodegradable compounds.
- Electrochemical Disinfection:
- Used for the disinfection of biologically treated wastewater, enabling direct reuse of domestic water.
- Insoluble Electrode Manufacturing:
- The robust, chemically inert nature of BDD makes it ideal for use as an insoluble electrode in various industrial electrochemical processes.
- Sensor Technology:
- The wide potential window and stable surface properties of the BDD films make them excellent candidates for use in advanced electrochemical sensors.
- Industrial Coating Scaling:
- The HFCVD method employed is highly suitable for industrial scaling, allowing for the production of large-area BDD electrodes at a lower cost than competing deposition techniques.
View Original Abstract
Diamond coating using hot-filament chemical vapor deposition (HFCVD) is now widely used in many fields. The quality of the diamond film and many factors determine the success of the coating, such as temperature, time, and pressure during coating. The purpose of this study was to produce coated boron-doped diamond (BDD) films by doping boron in the diamond film and to assess them through comparative analysis with foreign acid BDD, which is widely used as a water-treatment electrode in the present industry. The bending of the titanium substrate due to the high temperature during the diamond deposition was avoided by adding an intermediate layer with a columnar structure to niobium film. The filament temperature and pressure were determined through preliminary experiments, and BDD films were coated. The BDD film deposition rate was confirmed to be 100 nm/h, and the potential window increased with increasing thickness. The electrochemical activation and catalytic performance were confirmed according to the surface characteristics. Although the high deposition rate of the BDD coating is also an important factor, it was confirmed that conducting coating so that amorphous carbonization does not occur by controlling the temperature during coating can improve the electrochemical properties of BDD film.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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