Chemometric Raman Spectral Analysis of Diamond-like Carbon Films Deposited by Plasma Discharge
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-06-25 |
| Journal | Journal of Photopolymer Science and Technology |
| Authors | Yoshihisa Osano, Hiroyuki Fukue, Susumu Takabayashi, Shinsuke Kunitsugu, Yuichi Imai |
| Institutions | Okayama University of Science, Engineering Systems (United States) |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Chemometric Raman Analysis of Carbon Films
Section titled âTechnical Documentation & Analysis: Chemometric Raman Analysis of Carbon FilmsâExecutive Summary
Section titled âExecutive SummaryâThis research validates a highly efficient and reproducible chemometric approach for the five-peak separation analysis of Diamond-Like Carbon (DLC) Raman spectra, offering significant advantages for materials characterization and quality control.
- Methodology Advancement: Successfully replaced the computationally complex Voigt function with a modified pseudo-Voigt function combined with Nonlinear Least Squares (NLS) fitting.
- Computational Efficiency: The pseudo-Voigt function reduced average execution time to less than 20% of the conventional Voigt function, enabling rapid, automated analysis.
- Accuracy Improvement: Automated NLS fitting consistently achieved higher fitting accuracy (higher R2 and lower chi-squared, e.g., R2 = 0.99486 for HF-HiPIMS) compared to conventional manual fitting.
- Reproducibility: The automated Python-based NLS method eliminates reliance on analyst expertise, ensuring consistent interpretation of complex carbon structures (sp3 C-C and sp2 C=C bonds).
- Relevance to 6CCVD: This high-precision analytical technique is directly applicable to the quality control and structural verification of 6CCVDâs Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) materials, particularly for assessing crystal quality, stress, and doping uniformity.
- Deposition Techniques: DLC films were successfully characterized after deposition using two distinct methods: High-Frequency High-Power Impulse Magnetron Sputtering (HF-HiPIMS) and Alternating Current High Voltage Chemical Vapor Deposition (AC-HV-CVD).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental setup and analysis results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Deposition Method 1 | HF-HiPIMS | N/A | Non-hydrogenated DLC |
| Target Material | Graphite | N/A | 3-inch diameter |
| Operating Pressure (HF-HiPIMS) | 0.5 | Pa | Sputtering environment |
| Negative Applied Voltage | -810 | V | HF-HiPIMS setup |
| Overall Frequency | 200 | Hz | HF-HiPIMS waveform |
| Main Discharge Time (T3) | 50 | ”s | Pulse timing |
| Deposition Method 2 | AC-HV-CVD | N/A | Hydrogenated DLC |
| AC Voltage | 5 | kV | Deposition parameter |
| Offset Voltage | 2 | kV | Deposition parameter |
| Operating Pressure (AC-HV-CVD) | 39 | Pa | CVD environment |
| CH4 Gas Flow Rate | 96 | sccm | Carbon source gas |
| Raman Analysis | N/A | N/A | Chemometric fitting |
| Laser Wavelength | 532 | nm | Raman spectrometer |
| Laser Output Power | 0.5 | mW | Raman analysis |
| Spot Diameter | 2.55 | ”m | Measurement resolution |
| R2 (Pseudo-Voigt vs. Voigt) | 0.99996 | N/A | Function equivalence |
| Execution Time Reduction | < 20 | % | Pseudo-Voigt vs. Voigt |
| R2 (Automated NLS, HF-HiPIMS) | 0.99486 | N/A | Highest fitting accuracy achieved |
Key Methodologies
Section titled âKey MethodologiesâThe research employed two distinct deposition techniques for DLC film creation and a sophisticated chemometric approach for spectral analysis.
Deposition Parameters
Section titled âDeposition Parametersâ-
High-Frequency High-Power Impulse Magnetron Sputtering (HF-HiPIMS):
- Target: 3-inch diameter Graphite.
- Distance: Target-to-substrate distance of 100 mm.
- Gas: Argon (Ar) sputtering gas at 5 sccm flow rate.
- Pressure: Base pressure 5 x 10-4 Pa; Operating pressure 0.5 Pa.
- Voltage/Frequency: Negative applied voltage of -810 V; Overall frequency of 200 Hz.
-
Alternating Current High Voltage Chemical Vapor Deposition (AC-HV-CVD):
- Plasma Source: Methane (CH4) plasma.
- Voltage: AC voltage set to 5 kV with an offset voltage of 2 kV.
- Gas Flow: CH4 gas flow rate of 96 sccm.
- Pressure: Operating pressure of 39 Pa.
Chemometric Raman Analysis Procedure
Section titled âChemometric Raman Analysis Procedureâ- Data Loading and Preprocessing: Spectral data is loaded, and the analysis range is defined.
- Peak Identification: Differential spectrum method is applied to accurately identify peak positions.
- Normalization: Baseline removal and normalization are performed.
- Nonlinear Least Squares (NLS) Fitting: The Levenberg-Marquardt algorithm is used for automated fitting.
- Function Selection: A modified pseudo-Voigt function is used as the primary fitting function, replacing the complex Voigt function.
- Five-Peak Separation: The analysis utilizes a five-peak separation model (N, D, G-, G+, Dâ) derived from structural symmetry operations to accurately quantify sp3 and sp2 bond characteristics.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe high-precision Raman analysis detailed in this paper is crucial for advanced carbon material research. 6CCVD provides the foundational MPCVD diamond materials necessary to replicate, extend, and benchmark this type of structural characterization.
Applicable Materials for Advanced Spectroscopic Research
Section titled âApplicable Materials for Advanced Spectroscopic Researchâ| 6CCVD Material | Relevance to Research | Customization Potential |
|---|---|---|
| Optical Grade SCD | Ideal for use as a high-purity, low-defect reference standard for calibrating Raman systems and validating chemometric models against a known, near-perfect sp3 structure (Ra < 1nm polishing standard). | Available in thicknesses from 0.1 ”m to 500 ”m, suitable for both thin-film and bulk analysis. |
| High Purity PCD | Excellent for large-area applications (up to 125mm wafers) where structural uniformity and stress distribution must be mapped using automated Raman techniques. | Custom dimensions up to 125mm diameter are available, exceeding standard industry sizes. |
| Boron-Doped Diamond (BDD) | Essential for extending this research to electrically conductive carbon films, where BDDâs unique Raman shifts can be analyzed using the NLS five-peak model to quantify doping levels and activation. | Customizable doping concentrations and thicknesses (up to 500 ”m) for electrochemical and sensing applications. |
Customization Potential & Engineering Support
Section titled âCustomization Potential & Engineering Supportâ6CCVD is uniquely positioned to support researchers and engineers requiring highly specific diamond materials for advanced characterization projects:
- Custom Dimensions and Substrates: While the paper focused on 3-inch targets, 6CCVD offers PCD plates/wafers up to 125mm. We can provide custom-cut substrates (up to 10mm thick) tailored for specific deposition chambers or analytical setups.
- Precision Polishing: Achieving accurate Raman data requires minimal surface scattering. 6CCVD guarantees ultra-low roughness polishing: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD, optimizing signal quality for high-resolution spectroscopy.
- Integrated Metalization Services: If the DLC films or diamond substrates are intended for device integration (e.g., sensors or electronics), 6CCVD offers in-house metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu layers, applied with high precision.
- Expert Engineering Support: 6CCVDâs in-house PhD team specializes in MPCVD diamond growth and characterization. We can assist customers in selecting the optimal diamond material (SCD vs. PCD, doping level, orientation) required for similar Raman Spectroscopy and Chemometric Analysis projects, ensuring the material quality meets the demands of high-accuracy NLS fitting protocols.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
In this study, a chemometric approach for five-peak separation analysis of the Raman spectra of diamond-like carbon (DLC) films was investigated. DLC films were deposited by high-frequency inclusion high-power impulse magnetron sputtering and alternating current high voltage burst plasma chemical vapor deposition. We used the pseudo-Voigt function as an alternative to the conventional Voigt function and applied the nonlinear least squares method. The results not only facilitate automated analysis but also guarantee highly accurate results regardless of the analystâs level of expertise. This approach is expected to lead to consistent interpretation of Raman spectral analysis of DLC films and further research and understanding of the properties of DLC films.