Effects of Substrate Bias Voltage on Structure of Diamond-Like Carbon Films on AISI 316L Stainless Steel - A Molecular Dynamics Simulation Study

At a Glance

Metadata	Details
Publication Date	2021-08-30
Journal	Materials
Authors	Ngoc-Tu Do, Van‐Hai Dinh, Le Van Lich, Hong-Hue Dang-Thi, Trong‐Giang Nguyen
Institutions	Hanoi University of Industry, Hanoi University of Science and Technology
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: High sp³ Diamond Materials for Protective Coatings

This document analyzes the findings of the research paper, “Effects of Substrate Bias Voltage on Structure of Diamond-Like Carbon Films on AISI 316L Stainless Steel,” and aligns the material requirements with 6CCVD’s advanced MPCVD diamond capabilities.

Executive Summary

This molecular dynamics (MD) study confirms the critical role of substrate bias voltage ($V_{s}$) in controlling the microstructure and hybridization ratio of Diamond-Like Carbon (DLC) films deposited on AISI 316L stainless steel.

Structure Control: Substrate bias voltage is the primary mechanism for tuning the $sp^{3}$/$sp^{2}$ hybridization ratio, which dictates the mechanical and electrical properties of the DLC film.
Optimal Conditions: A bias voltage of 120 V resulted in the highest $sp^{3}$ fraction (48.5%), yielding a compact film structure and smooth surface morphology.
Superior Performance: The maximum $sp^{3}$ fraction achieved (48.5%) is significantly higher than films deposited on pure $\gamma$-Fe substrates (26.2%), validating the use of complex stainless steel alloys.
Application Relevance: The ability to control $sp^{3}$ content (ranging from 28.5% to 48.5%) is essential for tailoring DLC films for high-performance applications, including corrosion-resistant biomedical implants and conductive electrode materials.
6CCVD Value Proposition: While the research optimizes DLC (amorphous carbon), 6CCVD provides Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) materials with 100% $sp^{3}$ hybridization, offering inherently superior properties for the target applications (hardness, corrosion resistance, biocompatibility).

Technical Specifications

The following hard data points were extracted from the MD simulation results regarding DLC film characteristics:

Parameter	Value	Unit	Context
Optimal Substrate Bias Voltage ($V_{s}$)	120	V	Yields maximum $sp^{3}$ fraction and compact structure.
Maximum $sp^{3}$ Hybridization Fraction	48.5	%	Achieved at $V_{s}$ = 120 V.
Controllable $sp^{3}$ Fraction Range	28.5 to 48.5	%	Tunable across $V_{s}$ range of 0 V to 300 V.
First Radial Distribution Function (RDF) Peak	1.54	Å	Corresponds to short-range C-C diamond bonding.
Second RDF Peak	2.54	Å	Corresponds to short-range C-C diamond bonding.
Substrate Material Composition (Fe:Cr:Ni)	69.6:18.1:12.3	N/A	Mole fraction ratio of the AISI 316L substrate model.
Incident Carbon Atom Energy	15	eV/atom	Mimics typical magnetron sputtering conditions.
Substrate Temperature (Constant Zone)	300	K	Maintained during the deposition simulation.

Key Methodologies

The study utilized Molecular Dynamics (MD) simulations to model the growth process of DLC films on AISI 316L. The methodology focused on precise control over atomic interactions and deposition parameters.

Simulation Environment: Large-scale atomic/molecular massively parallel simulator (LAMMPS) code was used with periodic boundary conditions applied in the x and y directions.
Substrate Modeling: The AISI 316L substrate (36 Å x 36 Å x 15.6 Å) was divided into three zones: a fixed zone (bottom layer), a constant temperature zone (maintained at 300 K), and a relaxed zone (top layers).
Interatomic Potentials: A complex set of potentials was used to accurately model the multi-element system:
- Fe-Cr-Ni interactions: Embedded-Atom Method (EAM).
- C-C interactions: Tersoff potential.
- C-Ni interactions: Morse potential (fitted parameters: $D_{0}$ = 2.431 eV, $\alpha$ = 3.295 Å$^{-1}$, $r_{0}$ = 1.763 Å).
- (Fe, Cr)-C interactions: Tersoff/ZBL potential.
Deposition Parameters: 3000 C atoms were incident perpendicularly to the substrate surface with a kinetic energy of 15 eV/atom.
Bias Voltage Application: The substrate bias voltage ($V_{s}$) was simulated by applying an equivalent electric field perpendicular to the substrate, investigating values at 0 V, 120 V, and 300 V.

6CCVD Solutions & Capabilities

The research highlights the demand for materials with high $sp^{3}$ content, smooth surfaces, and controlled interfaces for critical applications (biomedical, protective coatings, electrodes). 6CCVD provides MPCVD diamond, which inherently meets and exceeds the structural goals of this research by offering 100% $sp^{3}$ hybridization.

Applicable Materials for Replication and Extension

Application Requirement	6CCVD Material Recommendation	Technical Rationale
Maximum Hardness & Corrosion Resistance (Targeting high $sp^{3}$ content)	Single Crystal Diamond (SCD)	Provides the ultimate material solution with 100% $sp^{3}$ bonding, far surpassing the 48.5% achieved by optimized DLC films. Ideal for high-wear cutting tools and precision optics.
Large Area Protective Coatings (Industrial scale, molds, bipolar plates)	Polycrystalline Diamond (PCD)	Cost-effective solution for large substrates (up to 125 mm diameter). Offers exceptional hardness and chemical inertness for industrial protective coatings.
Electrochemical Applications (High conductivity, stability)	Boron-Doped Diamond (BDD)	Available in both SCD and PCD formats. BDD provides the required electrical conductivity and extreme corrosion resistance necessary for high-performance electrodes and bipolar plates mentioned in the paper.

Customization Potential for Advanced Research

The MD simulation emphasizes the complexity of the film-substrate interface and the need for precise surface control. 6CCVD’s in-house capabilities are designed to support researchers and engineers requiring highly customized diamond solutions:

Custom Dimensions: While the paper focuses on thin films, 6CCVD can supply SCD and PCD plates/wafers up to 125 mm in diameter, enabling scale-up for industrial applications like large-format bipolar plates.
Thickness Control: We offer precise thickness control for both SCD and PCD films, ranging from ultra-thin (0.1 µm) to thick substrates (up to 10 mm), allowing for optimization of mechanical stress and adhesion.
Interface Engineering (Metalization): The paper noted the complex mixing of Fe, Cr, Ni, and C atoms at the interface. 6CCVD offers internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) to create clean, high-adhesion interlayers, simplifying interface control compared to complex bias tuning.
Surface Finish: To achieve the “smooth surface” desired at 120 V bias, 6CCVD provides industry-leading polishing services:
- SCD: Surface roughness $R_{a}$ < 1 nm.
- Inch-size PCD: Surface roughness $R_{a}$ < 5 nm.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD growth and material characterization. We offer expert consultation to transition research findings—such as optimizing protective coatings for AISI 316L stainless steel or developing high-performance biomedical implants—from simulation to physical realization using 100% $sp^{3}$ diamond materials.

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

View Original Abstract

With the recent significant advances in micro- and nanoscale fabrication techniques, deposition of diamond-like carbon films on stainless steel substrates has been experimentally achieved. However, the underlying mechanism for the formation of film microstructures has remained elusive. In this study, the growth processes of diamond-like carbon films on AISI 316L substrate are studied via the molecular dynamics method. Effects of substrate bias voltage on the structure properties and sp3 hybridization ratio are investigated. A diamond-like carbon film with a compact structure and smooth surface is obtained at 120 V bias voltage. Looser structures with high surface roughness are observed in films deposited under bias voltages of 0 V or 300 V. In addition, sp3 fraction increases with increasing substrate bias voltage from 0 V to 120 V, while an opposite trend is obtained when the bias voltage is further increased from 120 V to 300 V. The highest magnitude of sp3 fraction was about 48.5% at 120 V bias voltage. The dependence of sp3 fraction in carbon films on the substrate bias voltage achieves a high consistency within the experiment results. The mechanism for the dependence of diamond-like carbon structures on the substrate bias voltage is discussed as well.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma14174925

References

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