First-principles calculation of diamond/Al interface properties and study of interface reaction
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Ping Zhu, Qiang Zhang, Huasong Gou, Pingping Wang, Puzhen Shao |
| Citations | 8 |
| Analysis | Full AI Review Included |
Technical Analysis & Documentation: Diamond/Aluminum Interface Control
Section titled âTechnical Analysis & Documentation: Diamond/Aluminum Interface ControlâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the research on diamond/aluminum (Al) composite interfaces, focusing on crystal orientation effects and stability under wet-heat conditions. The findings underscore the critical need for precise material control, a core capability of 6CCVDâs MPCVD diamond products.
- Interface Adhesion: First-principles calculations confirm that the Diamond (100)/Al (111) interface exhibits significantly stronger adhesion ($W_{ad} = 5.85$ J/m²), representing a 41% improvement over the Diamond (111)/Al (111) interface ($W_{ad} = 4.14$ J/m²).
- Bonding Mechanism: Superior bonding on the {100} face is driven by enhanced charge transfer and the preferential formation of strong Al-C chemical bonds.
- Stability Challenge: The interface reaction product, aluminum carbide (Al4C3), which promotes initial bonding, is highly susceptible to hydrolysis in humid environments.
- Performance Degradation: After 60 days of wet-heat treatment (70 °C, 90% R.H.), the composite experienced a 29.9% drop in thermal conductivity and a 40.1% reduction in bending strength.
- Material Design Imperative: Achieving stable, high-performance diamond/metal composites requires strict control over diamond crystal orientation and the implementation of strategies (e.g., barrier layers) to inhibit the formation and subsequent degradation of Al4C3.
- 6CCVD Value Proposition: 6CCVD provides high-purity Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) with guaranteed crystal orientation and custom metalization services, enabling engineers to design interfaces optimized for both strength and environmental stability.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the first-principles calculations and experimental validation of the diamond/Al composites:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Adhesion Work ($W_{ad}$) | 5.85 | J/m² | Diamond (100)/Al (111) Interface (Calculated) |
| Adhesion Work ($W_{ad}$) | 4.14 | J/m² | Diamond (111)/Al (111) Interface (Calculated) |
| Adhesion Improvement | 41 | % | (100) vs. (111) Interface |
| Interface Product | Al4C3 | N/A | Forms preferentially on {100} face |
| Wet-Heat Temperature | 70 | °C | 90% R.H. |
| Wet-Heat Duration | 60 | days | Performance testing |
| Thermal Conductivity Drop | 29.9 | % | After 60 days wet-heat treatment |
| Bending Strength Drop | 40.1 | % | After 60 days wet-heat treatment |
| Initial Bending Strength | 247.6 | MPa | Before wet-heat treatment |
| Final Bending Strength | 138.5 | MPa | After 60 days wet-heat treatment |
| Infiltration Temperature | 700 | °C | Vacuum gas pressure infiltration |
| Optimal C-Al Bond Length | 1.94 | Ă | Optimized C atom on Al (111) surface |
Key Methodologies
Section titled âKey MethodologiesâThe study combined advanced computational modeling with experimental synthesis and rigorous characterization to analyze the Diamond/Al interface.
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Computational Modeling (DFT):
- Software: Materials Studio 2017 (CASTEP module).
- Method: Density Functional Theory (DFT) using Ultrasoft pseudopotentials.
- Functionals: Generalized Gradient Approximation (GGA) in the Perdew-Burke-Ernzerhof (PBE) form.
- Optimization Criteria: Energy convergence to 1 x 10-5 eV/atom; force tolerance below 0.03 eV/Ă .
- Interface Models: Diamond (111)/Al (111) and Diamond (100)/Al (111) were constructed and optimized.
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Composite Synthesis:
- Raw Materials: 99.99% industrial pure Al (matrix) and MBD4 synthetic single crystal diamond particles (100 Âľm, reinforcement).
- Process: Vacuum Gas Pressure Infiltration.
- Parameters: Infiltration temperature of 700 °C; infiltration time of 30 min.
- Reinforcement Content: Diamond volume fraction approximately 60%.
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Structural and Chemical Characterization:
- Microscopy: Helios Nanolab600i SEM/FIB for morphology and sample preparation. Talos F200x TEM for high-resolution interface structure analysis.
- Surface Analysis: Dimension Icon AFM for surface roughness (Ra < 1nm for {111}, Ra < 5nm for {100}).
- Interface Product Identification: Alkali etching (to remove Al matrix) followed by SEM observation of Al4C3 pits on the diamond surface.
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Performance and Stability Testing:
- Thermal Properties: Thermal diffusivity ($k$) measured using LFA467Nanoflash. Thermal conductivity ($\lambda$) calculated using the mixing rule ($\lambda = k \times \rho \times c$).
- Mechanical Properties: Three-point bending tests (INSTRON-5569).
- Environmental Stability: Wet-heat aging in a constant temperature/humidity chamber (70 °C, 90% R.H.) for up to 60 days.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research clearly demonstrates that the performance and reliability of diamond/metal composites hinge on controlling the diamond crystal surface and mitigating detrimental interface reactions. 6CCVD is uniquely positioned to supply the necessary high-specification diamond materials and surface engineering required to replicate and advance this research, particularly for high-reliability thermal management applications.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the highest possible thermal performance and interface control, 6CCVD recommends the following materials:
| 6CCVD Material | Recommended Specification | Application Relevance |
|---|---|---|
| Single Crystal Diamond (SCD) | Optical Grade, High Purity (N < 1 ppm) | Ideal for fundamental research requiring precise orientation control ({100} or {111}) and maximum intrinsic thermal conductivity. |
| Polycrystalline Diamond (PCD) | Inch-size wafers (up to 125mm), 100 Âľm thickness | Scalable heat spreader applications where large area and high thermal performance are required, with controlled grain size. |
| Diamond Substrates | Up to 10 mm thickness | Used as robust carriers or bulk heat sinks in high-power electronic packaging. |
Customization Potential for Interface Engineering
Section titled âCustomization Potential for Interface EngineeringâThe study highlights two critical engineering challenges: crystal orientation selectivity and Al4C3 inhibition. 6CCVD offers direct solutions to both:
- Crystal Orientation Control: 6CCVD supplies SCD plates and wafers with guaranteed crystal orientations (e.g., {100} or {111} faces exposed). This allows researchers to selectively utilize the stronger bonding characteristics of the {100} face while applying targeted surface treatments.
- Custom Metalization for Barrier Layers: The instability of Al4C3 necessitates a diffusion barrier or wetting layer that prevents direct C-Al reaction. 6CCVD offers in-house metalization capabilities to deposit thin films that act as stable interface layers:
- Titanium (Ti) or Tungsten (W): Excellent carbide-forming layers that promote wetting and adhesion without forming the moisture-sensitive Al4C3 phase.
- Platinum (Pt) or Gold (Au): Used as capping layers for subsequent bonding or corrosion resistance.
- Surface Finish Optimization: The quality of the diamond surface is crucial for optimal interface contact during infiltration. 6CCVD guarantees ultra-low roughness:
- SCD Polishing: Ra < 1 nm.
- Inch-size PCD Polishing: Ra < 5 nm.
- Custom Dimensions and Thickness: 6CCVD can supply SCD and PCD materials in thicknesses ranging from 0.1 Âľm to 500 Âľm, and substrates up to 10 mm, tailored to the specific volume fraction and geometry required for vacuum gas pressure infiltration or other bonding techniques.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists specializes in MPCVD growth and diamond surface chemistry. We offer comprehensive engineering consultation to assist clients in:
- Selecting the optimal diamond material (SCD vs. PCD) based on required thermal conductivity and mechanical stability.
- Designing multi-layer metalization schemes (e.g., Ti/Pt/Au stacks) to inhibit detrimental interface phases like Al4C3 and ensure long-term stability in complex, humid environments.
- Optimizing surface preparation (polishing and cleaning) for high-reliability Diamond/Metal Composite projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
First-principles calculation and experimental methods are used to study the interfacial properties and reaction of diamond/Al composites. Based on the first-principles method, the interfacial adhesion work (<i>W</i><sub>ad</sub>), electronic structure and charge transfer of diamond/Al models are calculated systematically. The results show that the adhesion work of diamond(100)/Al(111) is 41% higher than that of diamond(111)/Al(111), therefore, the interface bonding of diamond(100)/Al(111) interface is stronger. According to the analysis of the electronic structure, there are more charges transferring at the diamond(100)/Al(111) interface, and the high charge density is distributed on the side of C atoms. The redistribution of charges at the interface is conducive to the formation of AlâC bond, so that the tendency of forming AlâC bonds is greater. The introduction of AlâC bond can promote the formation of CâC bond at the diamond(100)/Al(111) interface and improve the interfacial adhesion work. In addition, the diamond/Al composites are fabricated by vacuum gas pressure infiltration, and multi-scale characterization of the interface structure of diamond/Al composites is carried out. The interfacial debonding occurs mainly on the diamond {111}. Meanwhile, the interface product Al<sub>4</sub>C<sub>3</sub> is easier to form on the diamond {100}. The experimental phenomenon is consistent with the calculated results. Moreover, the influence of the interfacial reaction on the properties and stability of diamond/Al composites are further discussed through heat-moisture treatment. The study finds that the performance degradation in heat-moisture environment is related mainly to the hydrolysis of the interface product Al<sub>4</sub>C<sub>3</sub>. After 60 daysâ heat-moisture, the thermal conductivity of the diamond/Al composites decreases by 29.9%, and the bending strength is reduced by 40.1%. The large attenuation of performance is not conducive to the stability of composites in complex environments. Therefore, inhibiting the formation of Al<sub>4</sub>C<sub>3</sub> and improving interfacial selectivity are of great importance in developing the performance and stability of diamond/Al composites. The research in this paper not only lays a theoretical foundation for the first-principles calculation of the interface properties of diamond/metal, but also possesses important guidance significance in designing the diamond/metal composites.