Effect of Seed Size, Suspension Recycling and Substrate Pre-Treatment on the CVD Growth of Diamond Coatings
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-01-01 |
| Journal | Open Journal of Applied Sciences |
| Authors | A.K. Mallik, Sandip Bysakh, R. Bhar, Shlomo Rotter, Joana Catarina Mendes |
| Institutions | Jadavpur University, Central Glass and Ceramic Research Institute |
| Citations | 6 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Enhanced PCD Nucleation via NNP
Section titled âTechnical Documentation & Analysis: Enhanced PCD Nucleation via NNPâThis documentation analyzes the key findings regarding diamond seed size, suspension management, and pre-treatment effects on MPCVD Polycrystalline Diamond (PCD) growth, positioning 6CCVDâs expertise and advanced material capabilities as the definitive solution for engineers and researchers in this field.
Executive Summary
Section titled âExecutive SummaryâThe research details a robust methodology (Novel Nucleation Process, NNP) for growing uniform PCD coatings on silicon, emphasizing the critical interplay between substrate pre-treatment and seeding characteristics.
- Validated Process: The NNP (HFCVD Pre-Treatment + Ultrasonic Seeding + MPCVD Growth) is confirmed to significantly enhance PCD nucleation, enabling the deposition of uniform films.
- Optimal Seeding Grit: Sub-micron diamond particles (0.25 ”m) were identified as the most effective seeding material, yielding grain sizes down to 1.21 ”m while maintaining high PCD quality.
- High Film Quality Achieved: Optimized parameters produced high-quality PCD coatings with crystallinity ratings up to 94.93% (FWHM 3.40 cm-1) and minimal internal tensile stress (0.26 GPa).
- Recycling Limitation: The study exposed a severe limitation in feedstock management: reusing the diamond seeding suspension more than five times drastically degrades film quality (down to 60%) and results in discontinuous substrate coverage.
- Large Area Feasibility: The experiments utilized a 915 MHz, 8 kW MPCVD reactor, demonstrating scalability potential which directly aligns with 6CCVDâs large-area fabrication capabilities (up to 125 mm PCD).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points define the optimal experimental parameters and material quality achieved in the reported study.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| CVD Reactor Type (Growth) | MPCVD | (915 MHz) | Lambda DT1800 |
| Microwave Input Power (GC) | 8 | kW | Growth Condition (GC) |
| Substrate Temperature (GC) | 1050 | °C | Growth Condition (GC) |
| Chamber Pressure (GC) | 110 | Torr | Growth Condition (GC) |
| Gas Flow Ratio (CH4:H2) | 10 : 500 | sccm | Methane:Hydrogen |
| Optimal Seeding Grit Size | 0.25 | ”m | Sub-micron slurry |
| Substrate Pre-Treatment (PT) | HFCVD | (30 min) | 1% CH4/H2, 30 Torr, 600 °C |
| Highest PCD Quality | 94.93 | % | Raman Quality (Sample 4-1) |
| Lowest FWHM (Crystallinity) | 3.40 | cm-1 | Excellent crystal quality |
| Lowest Internal Stress | 0.26 | GPa | Tensile (Sample 1-3) |
| Average Grain Size (Range) | 1.21 to 2.84 | ”m | Dependent on grit size and suspension age |
| Recycling Limit (Before Failure) | 5 | cycles | Suspension reuse leads to quality drop (60%) |
Key Methodologies
Section titled âKey MethodologiesâThe synthesis employed a modified Novel Nucleation Process (NNP) involving three primary stages: Substrate Pre-Treatment, Ultrasonic Seeding, and Microwave Plasma CVD Growth.
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Substrate Preparation:
- Material: p-type Silicon (Si) wafers, 0.5 mm thick, cut into 25 mm2 pieces.
- Purpose: Silicon is chosen due to lattice compatibility and wide use in device fabrication.
-
HFCVD Pre-Treatment (PT):
- System: Hot Filament CVD (HFCVD).
- Recipe: 30 minutes exposure under diamond growth conditions (1% CH4/H2 gas flow, 30 Torr pressure, 600 °C).
- Effect: Forms a thin (10 - 15 nm) sp3 enriched carbon film on the Si surface, enhancing nucleation sites and reducing incubation time.
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Ultrasonic Seeding (US):
- Suspensions: Five batches of diamond micron grits were prepared (0.25 ”m up to 40-60 ”m).
- Procedure: Substrates (with and without PT) were seeded in an ultrasonic bath.
- Test Parameter: Each suspension was reused ten successive times to evaluate the effect of suspension aging/recycling.
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Microwave Plasma CVD Growth (GC):
- System: 915 MHz MPCVD reactor (DT1800).
- Conditions: 10 sccm CH4 + 500 sccm H2 at 110 Torr, utilizing 8 kW microwave power, maintaining a 1050 °C substrate temperature.
- Outcome: Synthesis of Polycrystalline Diamond (PCD) coatings.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to assist researchers and industrial engineers in replicating and expanding upon this successful NNP methodology, particularly regarding large-area uniformity, high crystallinity, and custom substrate handling.
Applicable Materials
Section titled âApplicable MaterialsâThe requirements identified in this research are perfectly suited to 6CCVDâs core catalog and specialized materials:
- MPCVD Polycrystalline Diamond (PCD) Wafers: 6CCVD offers high-quality PCD identical to the material synthesized in this study. We provide customizable thickness ranging from 0.1 ”m up to 500 ”m, suitable for high-power thermal management, protective coatings, and mechanical applications.
- Heavy Boron-Doped Diamond (BDD): For researchers aiming to extend the NNP technique to electrochemical or sensing applications, 6CCVD supplies custom BDD films grown via MPCVD, ensuring uniform doping profiles essential for conductivity and stability.
- High-Purity Substrates: While the paper used 25 mm2 Si pieces, 6CCVD routinely handles and processes large-area silicon and alternative substrate materials (e.g., Mo, W) for subsequent diamond deposition.
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs advanced fabrication and post-processing capabilities directly address the scalability, surface finish, and integration challenges inherent in complex CVD diamond processes:
| Requirement Addressed | 6CCVD Capability | Research Relevance |
|---|---|---|
| Large Area Uniformity | Custom dimensions up to 125 mm PCD wafers/plates. | Directly enables scale-up from 25 mm2 pieces to industrial wafer sizes. |
| Surface Quality | Precision polishing services for PCD: Ra < 5 nm (for inch-size wafers). | Ensures optimal surface finish for post-processing and device integration, often required after high-temp growth. |
| Material Thickness Control | SCD and PCD thickness control from 0.1 ”m to 500 ”m. Substrates up to 10 mm thickness. | Allows precise control over film mechanical properties and thermal characteristics (e.g., thin films for sensors or thick films for heat sinks). |
| Device Integration | In-house custom metalization (Au, Pt, Pd, Ti, W, Cu) and precision laser cutting. | Facilitates electrode creation or heat spreading layers, crucial for integrating PCD into device structures (addressing the PT layer function). |
Engineering Support
Section titled âEngineering SupportâThe findings regarding the rapid deterioration of seeding suspension effectiveness highlight the critical need for tight process control and high-quality feedstock management.
- 6CCVDâs in-house PhD engineering team specializes in optimizing MPCVD recipes and pre-treatment protocols (like NNP) to maximize nucleation density and minimize material waste.
- We offer consultation on selecting the ideal sub-micron diamond seed feedstock and developing proprietary slurry management protocols to ensure continuous, high-quality production of uniform, conformal PCD coatings, overcoming the recycling limitation identified in the paper.
- We provide global support with DDU default shipping and DDP options available worldwide, simplifying logistics for international research programs.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
CVD growth of uniform conformal polycrystalline diamond (PCD) coatings over complex three dimensional structures is very important material processing technique. It has been found that the nucleation and subsequent growth period is very critical for successful development of CVD diamond based technologies. There are many methods of enhancing diamond nucleation on foreign substrates-ultrasonic treatment with diamond seed suspension being the best among them. A combination of ultrasonic seeding (US) technique with prior treatment (PT) of the substrate under CVD diamond growth conditions for brief period of time, has found to be very effective in enhancing the diamond nucleation during CVD growthâtogether they are known as NNP. But successive usage of the same seeding suspension up to ten cycles deteriorates the seeding efficiency. 6th seeding cycle onwards the silicon substrates are barely get covered by diamond crystallites. Five different diamond micron grits were used for seeding the silicon substrates and it is observed that US with the sub-micron particles (0.25 ÎŒm) is very effective in efficient nucleation of PCD on Si substrates. PT of the substrate somewhat negates the effect of successive use of the same seeding slurry but it is best to avoid recycling of the same seeding suspension using micron size diamond grits.