Combining nanostructuration with boron doping to alter sub band gap acceptor states in diamond materials
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-01-01 |
| Journal | Journal of Materials Chemistry A |
| Authors | Sneha Choudhury, Benjamin Kiendl, Jian Ren, Fang Gao, Peter Knittel |
| Institutions | University of WĂŒrzburg, Helmholtz-Zentrum Berlin fĂŒr Materialien und Energie |
| Citations | 25 |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Nanostructured Boron-Doped Diamond for Visible-Light Photocatalysis
Section titled âTechnical Documentation and Analysis: Nanostructured Boron-Doped Diamond for Visible-Light PhotocatalysisâPrepared for 6CCVD Engineers and Scientists
Executive Summary
Section titled âExecutive SummaryâThe analyzed research successfully demonstrates a synergistic strategyâcombining morphology engineering (nanostructuration) with high-concentration boron dopingâto control sub-bandgap electronic states in diamond materials, paving the way for sustainable visible-light photocatalysis.
- Core Achievement: Introduction of stable electron acceptor states near the valence band maximum (VBM) and surface states near the conduction band minimum (CBM), effectively reducing the energy required for photoexcitation from deep UV (5.5 eV) toward the visible spectrum.
- Mechanism Verified: Soft X-ray Absorption Spectroscopy (XAS) confirmed that the electronic states (peaks A and B) responsible for visible-light activity are surface-dominated defects induced by boron doping in nanostructured and polycrystalline materials (B:PCD-H, B:Dfoam-O).
- Morphology Dependence: Single Crystal (B:SCD-H) showed weak pre-edge features, confirming that surface area enhancement (PCD, foam, nanodiamonds) is critical for maximizing these localized defect states.
- Surface Termination Control: Hydrogen termination (H-termination) successfully passivated certain dangling bond states (demonstrated by B:Dfoam-H), proving that precise control over surface chemistry is vital for optimizing electronic properties.
- 6CCVD Value Proposition: 6CCVD is uniquely positioned to supply the foundational High-Doping Boron-Doped Diamond (BDD) films, plates, and custom surfaces (H- or O-terminated) required to replicate and scale this advanced photocatalytic research.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted, detailing material composition and measured unoccupied state energies, critical for correlating doping recipe with electronic performance.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Bulk Diamond Band Gap (Experimental) | 5.47 | eV | Standard reference value |
| Boron Concentration (B:PCD Film) | ca. 1 x 1021 (5670) | atoms cm-3 (ppm) | Measured by SIMS |
| Boron Concentration (B:SCD) | 300 | ppm | TISNCM commercial source |
| Boron Concentration (Milled B:ND) | ca. 1.8 x 1020 (1020) | atoms cm-3 (ppm) | Elemental Analysis |
| XAS Peak A (Acceptor State) | 282.5 | eV | Pre-edge, close to VBM, B-doping induced |
| XAS Peak B (Surface State) | 284.1 | eV | Pre-edge, close to VBM, B-doping induced |
| XAS Peak C (Amorphous Carbon) | 285.2 | eV | Ï* transition from sp2 carbon |
| XAS Peak D (Broad Shoulder) | 286.5 | eV | Close to CBM, observed in nanostructured BDD |
| XAS Peak E (Bulk Exciton) | 289.3 | eV | Characteristic bulk transition (1s to bulk exciton) |
| DFT Calculated Band Gap (Bulk Diamond) | 5.40 | eV | Using GGA/PBE functional |
| DFT Predicted H-Term. Surface State (B-Ads) | 2.1 | eV | Above Fermi Level (EF) |
| DFT Predicted Non-Term. Surface State (B-Ads) | 0.9 | eV | Above Fermi Level (EF) |
Key Methodologies
Section titled âKey MethodologiesâThe following is a condensed list of critical synthesis and treatment parameters used in the fabrication and analysis of the diverse boron-doped diamond materials:
- B:SCD-H Preparation: SCD (111) purchased with 300 ppm B content. Hydrogen termination achieved via H2-plasma at 200 mbar pressure and 2.2 kW microwave power for 5 minutes.
- B:PCD-H Film Growth: Films grown in an ellipsoidal MPCVD reactor using H2 and CH4 gases, with B(CH3)3 as the boron precursor. Target concentration 1 x 1021 atoms cm-3.
- B:PCD-H Hydrogenation: PC films were hydrogenated under 50 mbar H2 pressure for 15 minutes using 9 kW microwave power.
- B:Dfoam Synthesis: Prepared using 0.5 ”m silica spheres spin-coated onto a 4 ”m thick B:PCD layer. The process included dip-coating in H-terminated nanodiamond solution followed by overgrowth and repetition (3 layers total). Final boron concentration ca. 2835 ppm.
- B:Dfoam Cleaning: Silica spheres removed using hydrofluoric acid. Non-diamond content removed using a 3:1 mixture of sulfuric and nitric acid for 1.5 hours at elevated temperatures.
- B:ND Milling and Centrifugation: Starting material was 0.45 mm thick B:PCD electrode (Element Six). Milled to produce ND particles < 650 nm. Isolation of 30 nm and 50 nm particles achieved via centrifugation.
- B:ND-H Hydrogenation: Performed via MPCVD plasma (H2 flow: 198 sccm, pressure: 36 mbar, power: 800 W) for 1 hour 10 minutes on drop-cast NDs (60 ”L) on Si substrates.
- Characterization: Soft X-ray Absorption (XA) and Emission (XE) Spectroscopy conducted at the C K edge at the BESSY II Synchrotron, utilizing both surface-sensitive Total Electron Yield (TEY) mode and bulk-sensitive Partial Fluorescence Yield (PFY) mode.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is an industry leader in high-quality MPCVD diamond synthesis, capable of delivering the custom Boron-Doped Diamond (BDD) materials required to advance or replicate the findings of this research on engineered photocatalysts. We provide the foundational platforms for both film-based and nanostructured applications (foam, NDs).
Applicable Materials
Section titled âApplicable MaterialsâThe foundation of this advanced photocatalysis research relies on precise and high-concentration boron doping, a specialty of 6CCVD:
- Heavy Boron Doped Polycrystalline Diamond (BDD PCD): Required to match the high concentration (up to 1 x 1021 atoms cm-3) used in the PCD film and foam base layers. 6CCVD offers custom BDD PCD wafers up to 125 mm in diameter, perfect for scaling up electrode or catalytic membrane fabrication.
- High Purity Single Crystal Diamond (SCD): Required for fundamental studies on boron-induced defects without grain boundary interference. We provide research-grade SCD, including (111) orientation, which was specifically studied in this work.
- Custom Thickness/Morphology Base Plates: We can provide SCD and PCD substrates in thicknesses ranging from 0.1 ”m up to 500 ”m (films/wafers) or up to 10 mm (substrates), enabling replication of the specific base layer dimensions (e.g., the 4 ”m B:PCD layer used for foam creation).
Customization Potential for Photocatalysis Research
Section titled âCustomization Potential for Photocatalysis ResearchâAchieving the synergistic effect highlighted in the paper requires control over both bulk material properties and surface engineering. 6CCVD provides end-to-end customization to meet these demanding research requirements:
| Research Requirement | 6CCVD Capability & Solution | Technical Benefit |
|---|---|---|
| High Dopant Concentration | Precise Boron doping via B(CH3)3 precursor to achieve high-level BDD materials (1020-1021 atoms cm-3). | Ensures high density of sub-bandgap acceptor states (Peaks A & B). |
| Surface Termination Control | In-house plasma processing for highly controlled H-termination (C-H) or O-termination (C=O, C-OH). | Crucial for passivating dangling bonds or introducing specific surface groups (e.g., required to stabilize states in B:Dfoam-O). |
| Nanomaterial Foundation | Provision of thick BDD PCD electrodes (e.g., 0.45 mm used for milling) and high-quality, highly polished PCD (Ra < 5 nm) for subsequent mechanical treatment (milling/nanostructuring). | Provides the necessary precursor material for high surface area diamond morphology research (NDs, Dfoam). |
| Electrochemical Contacts | Custom, multi-layer metalization services (Ti, Au, Pt, Pd, W, Cu) to ensure robust, low-resistance ohmic contacts for photoelectrochemical testing (e.g., for reducing COâ at -1.9 V vs. SHE). | Facilitates integration into operational photoelectrocatalytic cells and reactor setups. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists specializes in optimizing MPCVD recipes for specific applications. We recognize that subtle changes in boron incorporation location (surface vs. bulk) and termination (H- vs. O-) drastically alter the sub-bandgap states.
6CCVDâs experts can assist with material selection and specification development for projects focused on COâ Reduction, Nitrogen Reduction, and Advanced Photoelectrochemistry, ensuring optimal correlation between synthesis parameters and required electronic structure (VBM/CBM position relative to the Fermi level).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Synergistic effect of nanostructuration and boron doping allows sub-bandgap electron acceptor states in diamond materials to be controlled.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 1993 - Photoelectrochemical Hydrogen Production