Micro-structural and optical properties of diamond-like carbon films grown by magnetic field-assisted laser deposition
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Yimin Lu, Yujie Wang, Manman Xu, Hai Wang, Lin Xi |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Magnetic Field-Assisted DLC Growth
Section titled âTechnical Documentation & Analysis: Magnetic Field-Assisted DLC GrowthâThis document analyzes the research on magnetic field-assisted Pulsed Laser Deposition (PLD) of Diamond-Like Carbon (DLC) films, focusing on micro-structural and optical property enhancement. The findings are leveraged to demonstrate how 6CCVDâs advanced MPCVD diamond materials (SCD, PCD, BDD) provide superior, scalable, and uniform solutions for high $sp^3$ content applications.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the use of an inhomogeneous magnetic field to enhance the diamond-like ($sp^3$) content in DLC films grown via PLD.
- Methodology: Pulsed Laser Deposition (PLD) of graphite was performed under varying magnetic fields (up to 840 mT) generated by permanent magnets placed beneath the Si substrate.
- Plasma Control: The magnetic field confines the C2+ plasma via the Lorentz force, inducing helical flight paths and concentrating high-energy ions toward the substrate center.
- Structural Enhancement: Plasma confinement increases local pressure on the growing film, promoting the conversion of $sp^2$ carbon clusters to the desired $sp^3$ structure, confirmed by a low $I_D/I_G$ ratio (as low as 0.331).
- Optical Improvement: Enhanced $sp^3$ content resulted in improved optical properties, including a high refractive index (n â 2.6) and a low extinction coefficient (k â 0.008) near the center.
- Key Challenge: High magnetic fields (B2, B3) caused severe non-uniformity in film thickness (up to 52.9% variation) and high internal stress, leading to film delamination at the center.
- Conclusion: Magnetic field assistance is effective for $sp^3$ enhancement but requires significant engineering adjustments (e.g., plasma shielding, non-synchronous rotation) to achieve uniform, high-quality coatings suitable for micro/nano-electronic applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the critical experimental parameters and resulting material properties extracted from the study.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Magnetic Field (B3) | 840 | mT | Highest field tested, caused central delamination. |
| Laser Wavelength | 248 | nm | UV Excimer Laser (PLD20). |
| Laser Pulse Width | 30 | ns | Nanosecond regime. |
| Laser Energy Density | 5.2 | J/cm2 | Focused on graphite target. |
| Base Vacuum Pressure | 1 x 10-4 | Pa | PLD growth environment. |
| Substrate Material | Single Crystal Silicon | N/A | 60 mm x 0.5 mm dimensions. |
| Refractive Index (n) Range | 2.56 - 2.63 | N/A | Measured at 1000 nm wavelength. |
| Extinction Coefficient (k) Range | 0.008 - 0.227 | N/A | Measured at 1000 nm wavelength. |
| Thickness Non-Uniformity (B2) | 52.9 | % | Calculated over 18 mm radius. |
| Lowest $I_D/I_G$ Ratio (S2, 0 mm) | 0.331 | N/A | Correlates to highest $sp^3$ content achieved. |
| Highest $I_D/I_G$ Ratio (S2, 18 mm) | 1.020 | N/A | Correlates to lowest $sp^3$ content (film edge). |
| G-Peak Position (S1, 0 mm) | 1570.8 | cm-1 | Indicates high local stress/pressure. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a specialized magnetic field-assisted PLD setup to control carbon plasma dynamics and enhance film properties.
- Ablation Source: A 248 nm, 30 ns UV excimer laser operating at 20 Hz was used to ablate a 99.99% pure graphite target at an energy density of 5.2 J/cm2.
- Substrate Configuration: A 60 mm x 0.5 mm Single Crystal Silicon substrate was placed 60 mm from the target. The substrate and the underlying permanent magnet were rotated synchronously.
- Magnetic Field Generation: Rectangular permanent magnets (80 mm x 60 mm, varying thickness) were placed directly beneath the substrate (z = 0 plane) to generate inhomogeneous fields (B1, B2, B3) up to 840 mT.
- Plasma Simulation: The flight path of C2+ ions was simulated using the Lorentz force equation (F = qB x v) and iterative calculation, confirming helical confinement and central accumulation.
- Film Characterization:
- Thickness/Uniformity: Surface interference patterns and ellipsometry were used to measure thickness distribution and non-uniformity ($\delta$).
- Optical Constants: Ellipsometry data was fitted using the GenOsc model to determine the refractive index ($n$) and extinction coefficient ($k$).
- Microstructure: Raman spectroscopy (532 nm laser) was performed, and spectra were deconvoluted into D (disorder) and G (graphitic) peaks to quantify the $sp^3/sp^2$ ratio via the $I_D/I_G$ ratio.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research successfully demonstrates methods to increase the $sp^3$ content in carbon films, aiming for diamond-like performance. 6CCVD specializes in manufacturing pure, high-quality MPCVD diamond, offering materials that inherently surpass the $sp^3$ content and uniformity challenges faced by the PLD-DLC method.
Applicable Materials for High-Performance Applications
Section titled âApplicable Materials for High-Performance Applicationsâ| Application Goal | 6CCVD Material Recommendation | Technical Rationale |
|---|---|---|
| Ultimate $sp^3$ Purity & Optical Clarity | Optical Grade Single Crystal Diamond (SCD) | Provides near-perfect $sp^3$ bonding (99.999%), eliminating the need for complex plasma confinement. Achieves superior thermal conductivity and ultra-low absorption (k < 10-4), far exceeding the DLC film performance (k â 0.008). |
| Large Area Coatings & Uniformity | High-Quality Polycrystalline Diamond (PCD) | Available in large plates/wafers up to 125 mm diameter. Our MPCVD process ensures exceptional thickness uniformity and low residual stress, directly solving the 52.9% non-uniformity and delamination issues encountered in the PLD study. |
| Electrochemical Sensing/Electrodes | Heavy Boron-Doped Diamond (BDD) | If the DLC films are intended for electrochemical applications (common for high $sp^3$ carbon), BDD offers unmatched chemical stability, a wide solvent window, and tunable conductivity, providing a robust, high-performance alternative. |
Customization Potential for Advanced Research
Section titled âCustomization Potential for Advanced ResearchâThe paper highlights the need for precise material control and integration. 6CCVD offers comprehensive customization services to meet the exact requirements of advanced research and device fabrication:
- Custom Dimensions and Thickness: We provide SCD and PCD plates in custom dimensions up to 125 mm. Thicknesses range from ultra-thin SCD/PCD films (0.1 ”m) up to robust substrates (10 mm).
- Precision Polishing: To achieve the low scattering required for optical applications (where $k$ is critical), 6CCVD offers industry-leading surface finishes:
- SCD: Ra < 1 nm
- Inch-size PCD: Ra < 5 nm
- Integrated Device Fabrication: We offer internal metalization capabilities, including deposition of Au, Pt, Pd, Ti, W, and Cu contacts. This is essential for integrating diamond films into micro/nano-electronic devices, addressing the application goals mentioned in the paper.
Engineering Support
Section titled âEngineering SupportâThe primary challenge identified in this research is managing internal stress and achieving uniformity while maximizing $sp^3$ content. 6CCVDâs in-house PhD team specializes in optimizing CVD growth parameters to control crystal quality, stress, and doping profiles.
We offer consultation services to researchers working on similar high-pressure carbon deposition projects, assisting with:
- Material selection for optimal thermal and optical performance.
- Designing custom diamond substrates for superior heat dissipation in high-power electronic devices.
- Developing specific metalization schemes for robust electrical contacts on diamond surfaces.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Inhomogeneous magnetic field is introduced into pulsed laser deposition process, in order to find new properties of diamond-like carbon film grown under magnetic field, thereby offering the theoretical and experimental basis for further enhancing sp<sup>3</sup>-bond content in this film. Distribution of the magnetic strength and flux lines induced by a rectangular permanent magnet is calculated. And then, flying trace of the carbon ions in the magnetic field is also simulated by the iterative method, which indicates that the carbon ions cannot expand freely and they are confined and accumulate around the center region of the magnet source. Beside the surface interference, the measurement and the fitted results of ellipsometry parameters show that magnetic field exerts an important influence on layer-thickness distribution and optical constant of the pulsed laser deposition-grown diamond-like carbon film. Meanwhile, it is indicated that the inhomogeneity of the layer-thickness distribution and optical constant increase when the magnetic strength is higher. Micro-structure of diamond-like carbon film is affected seriously by magnetic field, which is indicated by Raman spectra. Magnetic field can enhance the local stress in the carbon matrix net, increasing the sp<sup>3</sup>-bond content. Theoretical research and experimental research both show that a suitable magnetic strength can excite micro-structure of diamond-like carbon film significantly, and the high-quality diamond-like carbon coating with practical application value will be obtained by technological adjustment.