Diamond-coated ‘black silicon’ as a promising material for high-surface-area electrochemical electrodes and antibacterial surfaces
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2016-01-01 |
| Journal | Journal of Materials Chemistry B |
| Authors | Paul May, Michael A. Clegg, Tiago Almeida Silva, Hudson Zanin, Orlando Fatibello‐Filho |
| Institutions | Universidade Estadual de Campinas (UNICAMP), Oxford Instruments (United Kingdom) |
| Citations | 103 |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Diamond-Coated ‘Black Silicon’ Electrodes
Section titled “Technical Documentation and Analysis: Diamond-Coated ‘Black Silicon’ Electrodes”Document prepared for engineers and researchers seeking advanced Boron-Doped Diamond (BDD) solutions for high-surface-area electrochemical and biomedical applications.
Executive Summary
Section titled “Executive Summary”The analyzed research successfully demonstrates the use of high-aspect-ratio ‘black silicon’ (bSi) structures coated conformably with Boron-Doped Diamond (BDD) via CVD, resulting in materials optimized for high-sensitivity sensing and robust antibacterial applications.
- Record Surface Area Enhancement: The BDD coating on bSi long needles resulted in a relative effective electroactive surface area 221 times greater than that of a standard flat BDD electrode.
- Ultra-High Capacitance: Double-layer capacitance reached 638.0 µF cm-2, suggesting strong potential for highly efficient supercapacitor devices.
- High-Sensitivity Sensing: The structured BDD electrodes enabled sensitive and simultaneous detection of Dopamine (DA) and Uric Acid (UA) using DPV, achieving low Limits of Detection (LODs) of 0.27 µM (DA) and 2.1 µM (UA).
- Dual Functionality & Robustness: BDD-coated bSi demonstrated mechanical bactericidal activity (killing ~13% of P. aeruginosa cells) while offering superior scratch resistance and chemical stability compared to fragile bare silicon nanostructures.
- Tunable Performance: The electrochemical and bactericidal properties can be optimized by controlling the bSi needle length (1 µm vs. 15-20 µm) and the subsequent diamond deposition time (partial versus complete overgrowth).
- 6CCVD Capability Match: This material requires heavy BDD films deposited uniformly over complex, high-aspect-ratio substrates—a core competency of 6CCVD’s custom CVD material engineering.
Technical Specifications
Section titled “Technical Specifications”Extracted quantitative performance data and material characteristics from the research.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max Double-Layer Capacitance | 638.0 | µF cm-2 | Partially overgrown BDD/bSi long needles |
| Relative Effective Surface Area | 221 | N/A | Relative to commercial flat BDD control (1.0) |
| BDD Film Thickness | ~0.25 | µm | Deposited via HFCVD |
| Boron Doping Concentration | 2000 | ppm | B2H6 in gas phase (ensures near-metallic conductivity) |
| Short bSi Needle Length | 0.5-1 | µm | Optimal range suggested for mechanical cell destruction |
| Long bSi Needle Length | 15-20 | µm | Achieved highest capacitance/surface area |
| LOD (Dopamine, DA) | 0.27 | µM | Simultaneous DPV detection in presence of UA |
| LOD (Uric Acid, UA) | 2.1 | µM | Simultaneous DPV detection in presence of DA |
| Substrate Size (Tested) | 1.0 x 1.0 | cm2 | Cleaved from larger n-doped Si (100) wafers |
| Bacterial Kill Rate (P. aeruginosa) | ~13 | % | Achieved by BDD-coated short needles |
Key Methodologies
Section titled “Key Methodologies”The following high-level process steps and critical recipe parameters were utilized to fabricate the diamond-coated high-surface-area electrodes.
- Substrate Preparation (Black Silicon Etching):
- N-doped single-crystal silicon (100) wafers were used.
- Long Needle Etch (Cryogenic): Inductively Coupled Plasma (ICP) etching utilizing SF6 (60 sccm), O2 (10 sccm), 10 mTorr pressure. Critical process parameters included 800 W ICP power and an extremely low electrode temperature of -110 °C.
- Seeding:
- Electrospray process used Detonation Nanodiamond (DND) suspension in methanol.
- High potential difference (35 kV) ensured uniform, near-monolayer coating of the high-aspect-ratio bSi structures (~10 nm seeds).
- BDD Film Growth (Hot Filament CVD):
- Reactor Conditions: 20 Torr pressure, Tantalum filament temperature 2400 K, Substrate temperature ~900 °C.
- Microcrystalline BDD (MCD) Recipe: 1% CH4/H2 gas mixture, heavily doped with 2000 ppm B2H6.
- Nanocrystalline BDD (NCD) Recipe: 4% CH4/H2 gas mixture, heavily doped with 2000 ppm B2H6.
- Growth Result: Short deposition times (~1 hour) resulted in conformal coating; longer times (~2 hours) resulted in partial overgrowth and porous flat films.
- Surface Treatment (for Antibacterial Tests):
- Samples were acid washed (concentrated H2SO4, 80 °C) followed by retermination in H2 gas within the HFCVD reactor to ensure stable, robust hydrogen-termination (H-termination).
- Electrochemical Analysis:
- Cyclic Voltammetry (CV) measured double-layer capacitance using KNO3 or K3[Fe(CN)6]/KCl.
- Differential Pulse Voltammetry (DPV) was used for simultaneous detection of DA and UA in phosphate buffer solution (pH = 7.0).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is positioned to supply and engineer the critical diamond materials necessary to replicate, optimize, and scale this high-impact research into commercial reality. Our specialization in highly controlled MPCVD growth ensures superior film uniformity and purity required for reliable electrochemical and biomedical devices.
Applicable Materials
Section titled “Applicable Materials”To replicate the high-performance electrodes described, researchers require high-quality, heavily doped diamond. 6CCVD offers the necessary materials produced by high-uniformity MPCVD:
| 6CCVD Material | Description | Relevance to Paper’s Application |
|---|---|---|
| Heavy Boron-Doped NCD (Nanocrystalline Diamond) | High doping (up to 10,000 ppm B/C), ultra-smooth surface, uniform grain structure. | Suitable for high-area coatings requiring smoother, more rounded grains (as seen in the NCD films). Offers high sensitivity and low background current. |
| Heavy Boron-Doped PCD (Polycrystalline Diamond) | Customizable grain size (MCD equivalent), thickness up to 500 µm, high conductivity. | Required for achieving the highly conductive, near-metallic behavior necessary for advanced voltammetry and supercapacitor performance. |
| Custom Substrates and Seeding | Ability to coat non-standard or pre-structured substrates (such as customer-supplied bSi wafers) up to 125mm in diameter. | Crucial: We specialize in depositing highly conformal BDD films over complex, high-aspect-ratio topologies provided by the client (e.g., the bSi needles). |
Customization Potential
Section titled “Customization Potential”The success of this research hinges on precise control over material dimensions, doping, and surface properties. 6CCVD provides unparalleled control over these parameters:
- Substrate Compatibility: 6CCVD routinely processes standard Si wafers and can accept and coat customer-designed structured substrates (e.g., pre-etched bSi, carbon foam, or other micro/nano-patterned templates) up to 125mm diameter.
- Thickness Control: We guarantee high-precision thickness control for BDD films, ranging from ultra-thin 0.1 µm coatings (to preserve high surface area structure) up to 500 µm thick layers, allowing optimization between surface topology and mechanical robustness.
- Advanced Surface Termination: The antibacterial properties were optimized via Hydrogen (H) retermination. 6CCVD provides custom termination services (H-terminated, O-terminated) essential for specific biochemical interfacing projects.
- Integrated Metalization: For robust electrical connectivity and subsequent packaging (as copper/silver paste interfaces were used in the paper), 6CCVD offers in-house metalization (Au, Pt, Ti, Cu, W, Pd) deposition services, ensuring reliable ohmic contacts necessary for commercial sensor arrays.
Engineering Support
Section titled “Engineering Support”The enhanced performance of the BDD/bSi electrodes suggests high applicability in two major fields: Advanced Electrochemical Sensing (DA/UA detection) and Robust Biomedical/Antibacterial Surfaces.
6CCVD’s in-house PhD-level engineering team is available to assist customers in selecting optimal material specifications (doping level, grain size, surface termination) required to adapt this breakthrough for similar projects, including:
- Designing custom BDD layers for high-throughput neural interfacing applications (due to high capacitance).
- Optimizing diamond growth recipes (MCD vs. NCD) and thickness for maximal mechanical bactericidal efficacy and scratch resistance.
- Consulting on the integration of BDD films onto patterned substrates for enhanced supercapacitor energy storage devices.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Coating black silicon needles in a uniform layer of conducting boron-doped CVD diamond produces a high-surface-area electrode material that promising for electrochemical applications, as well as acting as a robust bactericidal surface.