Potential barrier heights at metal on oxygen-terminated diamond interfaces
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-11-25 |
| Journal | Journal of Applied Physics |
| Authors | Pierre Muret, Aboulaye Traoré, Aurélien Maréchal, David Eon, Julien Pernot |
| Institutions | Centre National de la Recherche Scientifique, Universidad de CĂĄdiz |
| Citations | 22 |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: Metal/Oxygen-Terminated Diamond Interfaces
Section titled âTechnical Analysis and Documentation: Metal/Oxygen-Terminated Diamond InterfacesâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the precise engineering of Schottky Barrier Diodes (SBDs) on oxygen-terminated, Boron-Doped Diamond (BDD) films, achieving tailored electrical properties critical for high-performance diamond electronics.
- Tailored Barrier Height ($\Phi_{B}$): The study achieved a significant reduction in the apparent barrier height from 1.83 V (unannealed) down to a near-ideal 0.97 V (after 450 °C annealing).
- Interface Control: Barrier height tuning is directly correlated with the chemical evolution and physical shrinkage of the interfacial Zirconium oxide (ZrO2) layer, evidenced by HRTEM and EELS (thickness reduced from 0.6 nm to 0.3 nm FWHM).
- Near-Ideal Performance: The optimized interfaces (450 °C anneal) exhibited near-ideal ideality factors (n = 1.00 to 1.07) and extremely low reverse current densities (down to 3 x 10-10 A/cm2 at 300 K).
- Material Foundation: The devices rely on high-quality, homoepitaxial p-type BDD films grown on Ib substrates, confirming the necessity of high-purity MPCVD diamond for advanced device fabrication.
- Advanced Modeling: The work utilizes sophisticated electrical models (generalizing Tungâs approach) to accurately account for barrier height inhomogeneities, providing deeper physical insight into metal-diamond interface physics.
- 6CCVD Value Proposition: 6CCVD provides the necessary high-quality, custom-doped, and polished Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) substrates required to replicate and scale this high-performance SBD technology.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material Base | Homoepitaxial BDD on Ib | N/A | Required for high-quality device layers |
| Diamond Orientation | (001) | N/A | Standard orientation for device fabrication |
| Active Layer Doping (NA) | 5 x 1015 | cm-3 | Lightly p-doped layer |
| Interface Termination | Oxygen | N/A | Achieved via UV-ozone treatment |
| Metal Contact | Zirconium (Zr) | N/A | Electron-gun deposited |
| Optimized Annealing Temperature | 450 | °C | Achieved lowest barrier height |
| Apparent Barrier Height ($\Phi_{B}$) (Unannealed) | 1.83 | V | At 300 K, Interface (a) |
| Apparent Barrier Height ($\Phi_{B}$) (450 °C Anneal) | 0.97 | V | At 300 K, Interface (c) |
| Oxide Interlayer Thickness (FWHM) (Unannealed) | 0.6 | nm | Measured via EELS |
| Oxide Interlayer Thickness (FWHM) (Annealed) | 0.3 | nm | Sharpened interface after 450 °C anneal |
| Ideality Factor (n) (450 °C Anneal) | 1.00 to 1.07 | N/A | Indicates near-ideal thermionic emission |
| Reverse Current Density (450 °C Anneal) | 3 x 10-10 | A/cm2 | Extremely low leakage current |
| Effective Richardson Constant ($\alpha A^{**}$) (450 °C) | 8.5 | A cm-2 K-2 | Derived from Richardson plot |
Key Methodologies
Section titled âKey MethodologiesâThe experimental success relied on precise control over material growth, surface preparation, and thermal processing, coupled with advanced nanoscale characterization.
- Diamond Growth: Homoepitaxial growth of a lightly boron-doped diamond layer on a heavily doped (p++) layer, itself grown on a high-quality Ib substrate (typical of MPCVD processes).
- Surface Preparation: The lightly doped surface was subjected to a photo-chemical UV-ozone treatment for two hours at room temperature to ensure prevailing oxygen terminations.
- Metal Deposition: Schottky junctions were formed by electron-gun deposition of Zirconium (Zr) in ultra-high vacuum (UHV).
- Thermal Treatment: Three interface types were created: (a) unannealed (< 300 °C), (b) annealed at 350 °C, and (c) annealed at 450 °C.
- Nanostructure Analysis: High Resolution Transmission Electron Microscopy (HRTEM) and Electron Energy Loss Spectroscopy (EELS) were used to identify the interfacial oxide layer (ZrO2) and measure its sub-nanometer thickness and chemical evolution.
- Electrical Characterization: Current-Voltage (I-V) characteristics were measured across a range of temperatures (300 K to 600 K) to derive the Richardson constant, ideality factor, and barrier height, enabling detailed modeling of interface inhomogeneities.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the foundational MPCVD diamond materials and advanced processing services necessary to replicate, optimize, and scale the high-performance diamond SBDs demonstrated in this research.
Applicable Materials
Section titled âApplicable MaterialsâThe research requires high-quality, homoepitaxial Boron-Doped Diamond (BDD) films with precise doping control.
- Material Recommendation: Boron-Doped Single Crystal Diamond (BDD SCD).
- Replication Fidelity: SCD offers the highest crystalline quality and lowest defect density, essential for the homoepitaxial growth stack used in the study.
- Custom Doping: 6CCVD provides custom BDD doping levels, allowing engineers to precisely match the required lightly doped (NA â 5 x 1015 cm-3) and heavily doped (p++) layers.
- Scale-Up Potential: Boron-Doped Polycrystalline Diamond (BDD PCD).
- For scaling device production, 6CCVD offers BDD PCD wafers up to 125 mm in diameter, enabling large-area device fabrication not possible with typical SCD substrates.
Customization Potential
Section titled âCustomization PotentialâThe success of this research hinges on precise control over the diamond surface and the metal/oxide interface. 6CCVD offers comprehensive services to meet these needs:
| Requirement from Paper | 6CCVD Capability | Technical Advantage |
|---|---|---|
| High Quality (001) Surface | Ultra-Low Roughness Polishing | SCD surfaces polished to Ra < 1 nm, ensuring optimal starting conditions for UV-ozone termination and subsequent Zr deposition. |
| Custom Doping Stacks | Custom Thickness & Doping Profiles | We supply SCD/PCD layers from 0.1 ”m to 500 ”m thick, allowing for the precise lightly-doped/heavily-doped stack architecture required for SBDs. |
| Metalization (Zr) | Custom Metalization Services | While Zr is not standard, 6CCVD offers in-house deposition of refractory metals like Titanium (Ti) and Tungsten (W), which are chemically similar carbide-forming metals suitable for diamond contacts. We also offer standard Au, Pt, Pd, and Cu metalization. |
| Device Geometry | Precision Laser Cutting & Shaping | We provide custom dimensions and shapes for plates and wafers, ensuring compatibility with specific device layouts and annealing setups. |
Engineering Support
Section titled âEngineering SupportâThe complex interplay between interface chemistry, thermal annealing, and electrical performance requires expert consultation.
- Interface Optimization: 6CCVDâs in-house PhD material science team specializes in diamond surface termination (including oxygen and hydrogen termination) and metal-diamond interface physics. We can assist researchers in optimizing the UV-ozone treatment and annealing recipes (350 °C to 450 °C) required for similar High-Performance Diamond Rectifier projects.
- Modeling Assistance: Our team understands the advanced electrical models (like the generalized R.T. Tung model) used to analyze barrier height inhomogeneities and can provide technical data and support to ensure accurate parameter extraction.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO2 deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprised of a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on an Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that by Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones, (b) annealed at 350 °C, (c) annealed at 450 °C with the characteristic barrier heights of 2.2-2.5 V in case (a) while as low as 0.96 V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients that are able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces.