Enhanced optoelectronic performances of vertically aligned hexagonal boron nitride nanowalls-nanocrystalline diamond heterostructures
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-07-11 |
| Journal | Scientific Reports |
| Authors | Kamatchi Jothiramalingam Sankaran, Duc Quang Hoang, Srinivasu Kunuku, Svetlana Korneychuk, Stuart Turner |
| Institutions | University of Antwerp, Tamkang University |
| Citations | 23 |
| Analysis | Full AI Review Included |
Enhanced Optoelectronic Performance of hBNNWs-nNCD Heterostructures: 6CCVD Technical Analysis
Section titled âEnhanced Optoelectronic Performance of hBNNWs-nNCD Heterostructures: 6CCVD Technical AnalysisâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the fabrication and performance enhancement of vertically aligned hexagonal boron nitride nanowalls (hBNNWs) using a nanocrystalline diamond (nNCD) interlayer, providing critical material specifications and linking them to 6CCVDâs MPCVD capabilities.
- Core Achievement: The use of nitrogen-doped nanocrystalline diamond (nNCD) as an interlayer significantly enhanced Field Electron Emission (FEE) and Plasma Illumination (PI) properties of hBNNWs heterostructures.
- Performance Metrics: The hBNNWs-nNCD structure achieved an ultra-low turn-on field (E0) of 15.2 V/”m and a high current density (Je) of 1.48 mA/cm2, far superior to hBNNWs grown directly on Si (E0 = 46.6 V/”m).
- Robustness: The heterostructure demonstrated exceptional life-time stability, maintaining emission for 248 minutes at 0.20 mA/cm2.
- Mechanism (Growth): The diamond interlayer facilitated the direct nucleation and growth of highly crystalline hBN, circumventing the formation of detrimental amorphous (aBN) and turbostratic (tBN) precursor phases observed on Si.
- Mechanism (Conduction): Nitrogen doping in the nNCD film induced sp2 graphite phases in the grain boundaries, creating percolative conduction paths that efficiently transport electrons to the hBNNWs interface.
- Application: The materials show promise for high-brightness electron sources and flat panel displays, demonstrated by a low plasma illumination threshold voltage of 370 V.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key performance metrics achieved by the optimal hBNNWs-nNCD heterostructure compared to the baseline hBNNWs-Si structure.
| Parameter | Value (hBNNWs-nNCD) | Value (hBNNWs-Si) | Unit | Context |
|---|---|---|---|---|
| Turn-on Field (E0) | 15.2 | 46.6 | V/”m | Lowest field required to induce FEE |
| FEE Current Density (Je) | 1.48 | 0.21 | mA/cm2 | Measured at applied field (E) |
| Applied Field (E) | 21.3 | 91.6 | V/”m | Field corresponding to Je measurement |
| Life-time Stability | 248 | 27 | min | Measured at Je ~0.20 mA/cm2 |
| Field Enhancement Factor (ÎČ) | 3057 | 560 | Dimensionless | Calculated from Fowler-Nordheim slope |
| Plasma Illumination (PI) Threshold Voltage | 370 | 460 | V | Voltage required to ignite microplasma |
| PI Current Density (Jp) | 2.46 | 0.57 | mA/cm2 | Measured at 500 V applied voltage |
Key Methodologies
Section titled âKey MethodologiesâThe heterostructures were fabricated using a two-step process involving Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) for the diamond layer and Radio Frequency (RF) sputtering for the hBNNWs.
1. Nanocrystalline Diamond (NCD/nNCD) Growth (MPECVD)
Section titled â1. Nanocrystalline Diamond (NCD/nNCD) Growth (MPECVD)â| Step | Parameter | Undoped NCD | Nitrogen-Doped nNCD |
|---|---|---|---|
| Reactor | Type | ASTeX 6500 series MPECVD | ASTeX 6500 series MPECVD |
| Substrate | Material | Mirror polished (100)-oriented Silicon (Si) | Mirror polished (100)-oriented Silicon (Si) |
| Seeding | Precursor | 5 nm detonation nanodiamond colloidal suspension | 5 nm detonation nanodiamond colloidal suspension |
| Gas Mixture | Flow Rate (sccm) | CH4 (3) / H2 (297) | CH4 (18) / H2 (267) / N2 (15) |
| Gas Ratio | CH4/H2 | 1/99 | 6/89/5 |
| Microwave Power | Power (W) | 3000 | 3000 |
| Pressure | Total (Torr) | 20 | 20 |
| Growth Temperature | Estimated (°C) | ~675 | ~540 |
2. hBN Nanowalls (hBNNWs) Growth (RF Sputtering)
Section titled â2. hBN Nanowalls (hBNNWs) Growth (RF Sputtering)â| Parameter | Value | Context |
|---|---|---|
| Technique | Unbalanced RF Sputtering (13.56 MHz) | Home-built system |
| Target | Pyrolytic BN ceramic (3 inch diameter, 99.99% purity) | Source material |
| Gas Mixture | Ar(51%) / N2(44%) / H2(5%) | Optimal fabrication condition |
| RF Power | 75 W | Cathode power |
| Working Pressure | 2.1 x 10-2 mbar | Low pressure environment |
| Growth Temperature | 125 °C | Low temperature process |
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research successfully demonstrates that high-performance electron emitters require highly controlled, conductive diamond interlayers. 6CCVD is uniquely positioned to supply the necessary materials and customization required to replicate, scale, and optimize this research for commercial application.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend the enhanced FEE performance demonstrated by the hBNNWs-nNCD heterostructures, 6CCVD recommends the following materials:
| 6CCVD Material | Description & Relevance to Research | Customization Potential |
|---|---|---|
| Polycrystalline Diamond (PCD) | Required for the nNCD interlayer. 6CCVD offers high-quality PCD films grown via MPCVD, allowing precise control over grain size (nanocrystalline range) and surface morphology (smoothness, critical for uniform hBNNW growth). | Custom Thickness: PCD films available from 0.1 ”m up to 500 ”m, enabling optimization of the interlayer thickness for electron transport. |
| Boron-Doped Diamond (BDD) | While the paper used Nitrogen (N) doping to enhance conductivity via sp2 phases, BDD is 6CCVDâs standard, highly conductive material. BDD provides superior, stable, bulk conductivity (p-type) necessary for efficient electron supply to the hBN interface, potentially surpassing the stability of N-doped films. | Doping Control: BDD films can be supplied with varying Boron concentrations (light to heavy doping) to tune resistivity for specific device requirements. |
| Optical Grade SCD/PCD Substrates | For applications requiring high thermal management or specific optical transparency, 6CCVD can supply the diamond interlayer as a free-standing substrate (up to 10 mm thick) or as a highly polished wafer. | Polishing: SCD (Ra < 1 nm) and inch-size PCD (Ra < 5 nm) polishing services ensure the ultra-smooth surfaces necessary for uniform nanowall nucleation. |
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs advanced MPCVD and post-processing capabilities directly address the engineering requirements of this high-performance heterostructure:
- Large Area Scaling: The paper utilized small Si wafers. 6CCVD can supply PCD plates/wafers up to 125 mm in diameter, enabling industrial scaling of these electron emitter arrays for flat panel displays or large-area cold cathodes.
- Custom Thickness Control: We offer precise control over the diamond interlayer thickness (0.1 ”m to 500 ”m) to optimize the interface resistance and overall device architecture.
- Advanced Metalization: Although the paper focused on the diamond/hBN interface, final device integration often requires contact layers. 6CCVD offers in-house metalization services (Au, Pt, Pd, Ti, W, Cu) for creating ohmic contacts or complex electrode patterns on the diamond surface prior to or after hBNNW growth.
- Precision Processing: Custom laser cutting and shaping services are available to produce specific cathode geometries or microplasma cavity structures, as referenced in the research.
Engineering Support
Section titled âEngineering SupportâThe successful enhancement of FEE relies on controlling the diamond microstructure (nanocrystalline grain size) and conductivity (doping).
- MPCVD Expertise: 6CCVDâs in-house PhD team specializes in tuning MPCVD parameters (gas ratios, pressure, temperature) to achieve specific diamond morphologies, such as the highly conductive nanocrystalline structure required for this Field Electron Emission project.
- Material Consultation: We provide expert consultation on selecting the optimal conductive diamond material (e.g., comparing the benefits of N-doped PCD vs. BDD) to maximize the field enhancement factor (ÎČ) and life-time stability for similar cold cathode applications.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive diamond materials, supporting international research and development efforts.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Field electron emission (FEE) properties of vertically aligned hexagonal boron nitride nanowalls (hBNNWs) grown on Si have been markedly enhanced through the use of nitrogen doped nanocrystalline diamond (nNCD) films as an interlayer. The FEE properties of hBNNWs-nNCD heterostructures show a low turn-on field of 15.2 V/ÎŒm, a high FEE current density of 1.48 mA/cm 2 and life-time up to a period of 248 min. These values are far superior to those for hBNNWs grown on Si substrates without the nNCD interlayer, which have a turn-on field of 46.6 V/ÎŒm with 0.21 mA/cm 2 FEE current density and life-time of 27 min. Cross-sectional TEM investigation reveals that the utilization of the diamond interlayer circumvented the formation of amorphous boron nitride prior to the growth of hexagonal boron nitride. Moreover, incorporation of carbon in hBNNWs improves the conductivity of hBNNWs. Such a unique combination of materials results in efficient electron transport crossing nNCD-to-hBNNWs interface and inside the hBNNWs that results in enhanced field emission of electrons. The prospective application of these materials is manifested by plasma illumination measurements with lower threshold voltage (370 V) and longer life-time, authorizing the role of hBNNWs-nNCD heterostructures in the enhancement of electron emission.