Fast, Efficient Tailoring Growth of Nanocrystalline Diamond Films by Fine-Tuning of Gas-Phase Composition Using Microwave Plasma Chemical Vapor Deposition

At a Glance

Metadata	Details
Publication Date	2024-06-18
Journal	Materials
Authors	C.J. Tang, A.J.S. Fernandes, M. Facão, Alexandre F. Carvalho, Weixia Chen
Institutions	Changshu Institute of Technology, University of Aveiro
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Rate Nanocrystalline Diamond (NCD) Growth

This document analyzes the research on fast, efficient tailoring of Nanocrystalline Diamond (NCD) films via Microwave Plasma Chemical Vapor Deposition (MPCVD) using N${2}$ and O${2}$ additives. It highlights 6CCVD’s capabilities to meet and exceed the material requirements for industrial and scientific applications, particularly in tribology and MEMS/NEMS.

Executive Summary

6CCVD, an expert supplier of MPCVD diamond materials, confirms that the research successfully demonstrates a highly efficient, scalable method for producing high-quality Nanocrystalline Diamond (NCD) films.

Record Growth Rates: Achieved high average NCD growth rates up to 6.7 µm/h (and 7.1 µm/h in specific runs), representing a significant increase (over 2x) compared to conventional Microcrystalline Diamond (MCD) growth under similar base conditions.
Process Optimization: Validated a new, extended operating parameter range for NCD synthesis by fine-tuning N${2}$ (0.5-1.6 sccm) and O${2}$ (0-3.0 sccm) additives in standard 4% CH${4}$/H${2}$ plasma.
Surface Quality: Produced NCD films exhibiting low Root Mean Square (RMS) surface roughness (as low as 291 nm), confirming suitability for low-friction and wear-resistant coatings.
Structural Control: Demonstrated precise control over film structure, achieving nanocrystalline grain sizes (31 ± 10 nm) and a desirable <110> preferred orientation.
Temperature Versatility: Confirmed the stability and reproducibility of NCD formation across a wide range of substrate temperatures (simulated 672 °C to 864 °C), crucial for large-area industrial processing.

Technical Specifications

The following hard data points were extracted from the experimental results, demonstrating the high performance achieved using optimized gas chemistry.

Parameter	Value	Unit	Context/Sample
Highest Average Growth Rate	6.7	µm/h	Sample DNO2 (1:1 N${2}$:O${2}$ ratio)
Maximum Observed Growth Rate	7.1	µm/h	Sample DN3 (1.6 sccm N$_{2}$ only)
NCD Grain Size (DNO2)	31 ± 10	nm	Calculated via Scherrer’s equation
Lowest RMS Surface Roughness (NCD)	291	nm	Sample DNO7 (5 mm thick Si substrate)
Base Gas Mixture	4% CH${4}$/H${2}$	Ratio	Fixed for all NCD runs
Operating Pressure	105	Torr	Fixed for all runs
Microwave Power Range	3.0 to 3.5	kW	Used in 5 kW MPCVD reactor
N$_{2}$ Additive Range	0.5 to 1.6	sccm	Explored range
O$_{2}$ Additive Range	0.0 to 3.0	sccm	Explored range
Substrate Temperature Range (Inferred)	672 to 864	°C	Simulated range based on Si thickness (1 mm to 5 mm)
Diamond Peak FWHM (MCD D4)	3.5	cm^-1	Reference MCD crystalline quality

Key Methodologies

The NCD films were fabricated using a high-power MPCVD system with precise control over gas phase composition and indirect temperature management.

High-Power MPCVD: Depositions were conducted in a 5 kW MPCVD reactor (ASTeX PDS-18) operating at high power (3.0-3.5 kW) and a fixed pressure of 105 Torr.
Base Chemistry: A standard 4% CH${4}$ in H${2}$ mixture was used as the primary reactant gas.
Additive Variation: Novel experimental series were designed by fixing N${2}$ flow (1 sccm) and varying O${2}$ flow (1 to 3 sccm), extending the parameter space beyond previous literature limits (1 sccm total additives).
Substrate Preparation: <100>-oriented single-crystal Si substrates were pre-scratched with 0-0.5 µm diamond powder to ensure high nucleation density, characteristic of NCD growth.
Indirect Temperature Control: Substrate surface temperature was systematically adjusted by three methods:
- Varying Si substrate thickness (1 mm, 3 mm, 5 mm).
- Slightly varying microwave power.
- Changing the Mo holder design (Type 1 vs. Type 2) to modify thermal contact area to the water-cooled base.
Structural Analysis: Comprehensive characterization included SEM (morphology, cross-section thickness), micro-Raman spectroscopy (sp² content, crystallinity), and XRD (preferred orientation, grain size calculation).

6CCVD Solutions & Capabilities

The research validates the commercial viability of high-rate NCD films for mechanical and electrochemical applications. 6CCVD is uniquely positioned to supply the materials and engineering expertise required to replicate and scale this technology.

Research Requirement/Challenge	6CCVD Solution & Capability	Technical Advantage & Sales Driver
High-Rate NCD Production (6.7 µm/h)	Polycrystalline Diamond (PCD) Materials. 6CCVD specializes in high-power MPCVD, capable of replicating the optimized N${2}$/O${2}$ chemistry to achieve high deposition rates for thick NCD films.	Rapid fabrication of thick NCD coatings (up to 500 µm) for industrial wear-resistant and tribological applications.
Large-Area NCD Uniformity	Custom Dimensions up to 125 mm (PCD). The paper used 2-inch wafers; 6CCVD scales this process to produce uniform PCD plates up to 125 mm in diameter.	Ensures industrial scalability for large-format MEMS/NEMS devices and coating processes. Global shipping (DDU/DDP) available.
Ultra-Smooth Surface Finish (RMS Sq 291 nm)	Advanced Polishing Services. While as-grown NCD is smooth, 6CCVD offers precision polishing to achieve Ra < 5 nm on inch-size PCD, surpassing the paper’s as-grown roughness.	Provides ultra-low friction surfaces necessary for high-performance tribology and critical sealing applications.
Tailored Crystallinity and Orientation	Custom MPCVD Recipe Development. Our engineering team can precisely control the N${2}$/O${2}$ gas ratios to tune grain size (e.g., 31 nm NCD) and preferred orientation (<110> texture), optimizing mechanical properties.	Guaranteed material specifications (grain size, texture) tailored to maximize hardness, fracture resistance, or specific electronic properties.
Functionalized NCD Films	Boron-Doped Diamond (BDD) Capability. For electrochemical or sensing applications (e.g., BDD electrodes), 6CCVD supplies BDD materials in NCD/UNCD morphology.	Provides highly conductive, chemically inert NCD films for advanced electrochemistry and sensor development.
Integrated Device Fabrication	Internal Metalization Services. If these NCD films require electrical contacts or bonding layers, 6CCVD offers custom metal stacks including Au, Pt, Pd, Ti, W, and Cu deposition.	Streamlined supply chain for engineers requiring ready-to-use diamond components with integrated metal contacts.

Engineering Support: 6CCVD’s in-house PhD team can assist with material selection and process optimization for similar high-rate NCD projects targeting wear-resistant coatings, MEMS/NEMS components, and advanced tribological systems.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Nanocrystalline diamond (NCD) films are attractive for many applications due to their smooth surfaces while holding the properties of diamond. However, their growth rate is generally low using common Ar/CH4 with or without H2 chemistry and strongly dependent on the overall growth conditions using microwave plasma chemical vapor deposition (MPCVD). In this work, incorporating a small amount of N2 and O2 additives into CH4/H2 chemistry offered a much higher growth rate of NCD films, which is promising for some applications. Several novel series of experiments were designed and conducted to tailor the growth features of NCD films by fine-tuning of the gas-phase compositions with different amounts of nitrogen and oxygen addition into CH4/H2 gas mixtures. The influence of growth parameters, such as the absolute amount and their relative ratios of O2 and N2 additives; substrate temperature, which was adjusted by two ways and inferred by simulation; and microwave power on NCD formation, was investigated. Short and long deposition runs were carried out to study surface structural evolution with time under identical growth conditions. The morphology, crystalline and optical quality, orientation, and texture of the NCD samples were characterized and analyzed. A variety of NCD films of high average growth rates ranging from 2.1 μm/h up to 6.7 μm/h were successfully achieved by slightly adjusting the O2/CH4 amounts from 6.25% to 18.75%, while that of N2 was kept constant. The results clearly show that the beneficial use of fine-tuning of gas-phase compositions offers a simple and effective way to tailor the growth characteristics and physical properties of NCD films for optimizing the growth conditions to envisage some specific applications.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma17122976

References

2021 - Achieving Large Uniform Tensile Elasticity in Microfabricated Diamond [Crossref]
2022 - Plastic Deformation in Silicon Nitride Ceramics via Bond Switching at Coherent Interfaces [Crossref]
2023 - In Situ Transmission Electron Microscopy Investigation on Oriented Attachment of Nanodiamonds [Crossref]
1997 - Nanocrystalline Diamond Films: Transmission Electron Microscopy and Raman Spectroscopy Characterization [Crossref]