| Metadata | Details |
|---|
| Publication Date | 2025-04-06 |
| Journal | Processes |
| Authors | Vilius Dovydaitis, Mindaugas MilieĹĄka, Johnny Chimborazo, Enrico Gnecco, Liutauras Marcinauskas |
| Institutions | Jagiellonian University, Universidad Yachay Tech |
| Citations | 2 |
| Analysis | Full AI Review Included |
- Objective: Investigate the impact of Chromium (Cr) concentration on the elemental composition, microstructure, and optical transparency of Diamond-like Carbon (DLC) films deposited via magnetron sputtering (MS).
- Compositional Trend: Increasing Cr content (from 7.4 at.% to 13.1 at.%) resulted in a significant, proportional increase in oxygen (O) concentration (from 34.6 at.% to 51.0 at.%), suggesting active Cr-O bond formation.
- Surface Morphology: The surface roughness (Ra) was optimally minimized (~10% reduction compared to pure DLC, Ra = 1.63 nm) at an intermediate Cr concentration of 9.2 at.%.
- Structural Changes (Graphitization): Raman spectroscopy indicated that Cr addition promoted graphitization (increased sp2 C=C bonds), evidenced by the G peak shifting to higher wavenumbers and a reduction in the G band dispersion (DG) from 0.206 cm-1/nm (pure DLC) to 0.109 cm-1/nm (highest Cr content).
- Optical Performance: Optical transmittance was reduced by up to 30% compared to pure DLC due to the enhanced sp2 bond fraction. However, the high co-doping of oxygen helped compensate for sp3 loss, maintaining transmittance values greater than 70% in the infrared (IR) wavelength range.
| Parameter | Value | Unit | Context |
|---|
| Deposition Method | Direct Current Magnetron Sputtering (DCMS) | N/A | Used 99.99% Cr and 99.9% Graphite targets |
| Substrates Used | Silicon (100) and Glass | N/A | Located 60 mm from magnetrons |
| Working Pressure (Ar) | 2-3 | Pa | Synthesis atmosphere |
| Base Pressure | < 0.01 | Pa | Chamber vacuum level |
| Graphite Target Current | 1.5 | A | Fixed deposition parameter |
| Chromium Target Current | 0.5 | A | Fixed deposition parameter |
| Film Thickness Range | 220 to 250 | nm | As-deposited films |
| Cr Concentration Range | 7.4 to 13.1 | at.% | Measured via EDS (Cr-DLC15 to Cr-DLC17) |
| Oxygen Concentration Range | 34.6 to 51.0 | at.% | Increased with Cr doping |
| Minimum Average Roughness (Ra) | 1.63 | nm | Achieved at 9.2 at.% Cr (Cr-DLC16) |
| Pure DLC Roughness (Ra) | 1.82 | nm | Baseline DLC film |
| G Peak Dispersion (DG) Range | 0.206 to 0.109 | cm-1/nm | Reduced with Cr increase (enhanced clustering) |
| Transmittance Reduction | Up to 30 | % | Compared to pure DLC coatings |
| Transmittance (Cr-DLC17, 500 nm) | 38 | % | Lowest visible light transparency |
| IR Transmittance (High Cr/O) | > 70 | % | Maintained in the infrared range |
| Raman Excitation Wavelengths | 458, 514, 633 | nm | Used for structural analysis |
- Deposition Setup: Films were deposited using Direct Current Magnetron Sputtering (DCMS) onto Si(100) and glass substrates.
- Target Materials: High-purity (99.99% Cr and 99.9% Graphite) 3-inch disc targets were used.
- Process Parameters: Graphite and Chromium target currents were set at 1.5 A and 0.5 A, respectively. The process was conducted in an Argon atmosphere at a working pressure of 2-3 Pa for 10 minutes.
- Pre-treatment: Cathodes were etched for 5 minutes in Ar plasma (2-3 Pa) after achieving a base pressure less than 0.01 Pa.
- Elemental Composition: Energy-Dispersive X-ray Spectroscopy (EDS) was performed using a 15 kV accelerating voltage over a 1.25 mm2 surface area.
- Surface Morphology: Atomic Force Microscopy (AFM) was used to measure the average (Ra) and root mean square (Rq) roughness.
- Bonding Structure Analysis: Micro-Raman spectroscopy was conducted using three distinct laser wavelengths (458 nm, 514 nm, and 633 nm) to determine the ID/IG ratio, G peak position, and G band dispersion (DG).
- Optical Transparency: Transmittance spectra were captured between 400 nm and 1300 nm using a UV-VIS-NIR spectrophotometer.
| Industry/Application | Technical Benefit Provided by Cr-DLC |
|---|
| Industrial Tooling & Molds | Enhanced mechanical and tribological performance (hardness, wear resistance) combined with improved adhesion due to Cr incorporation. |
| Automotive and Aerospace | Low coefficient of friction and excellent wear resistance for moving parts, crucial for reducing energy loss and extending component lifespan. |
| Optical Devices and Sensors | Controlled optical transparency in the VIS-NIR range. The high oxygen content allows for protective coatings that maintain high IR transmittance (>70%). |
| Corrosion Protection | Improved corrosion resistance, particularly relevant for components exposed to harsh environments, such as bipolar plates in Proton Exchange Membrane Fuel Cells (PEMFCs). |
| High-Stress Components | The ability to tailor the sp2/sp3 ratio and cluster size (via Cr doping) allows for the creation of coatings with optimized internal stress and elasticity modulus. |
View Original Abstract
Cr-doped diamond-like carbon (DLC) films were formed on silicon and glass substrates by magnetron sputtering (MS). The surface morphology, elemental composition, bonding structure, and transparency of the as-deposited films were analyzed by atomic force microscopy (AFM), the energy-dispersive X-ray spectroscopy (EDS), multiwavelength micro-Raman spectrometer, and UV-VIS-NIR spectrophotometer. The study revealed that the oxygen concentration in the Cr-DLC films increased as the Cr content increased. The surface roughness of the films was slightly reduced when the Cr content was ~9.2 at.%, and further increase in the Cr content up to 13.1 at.% stimulated the growth of the highest-roughness Cr-DLC films. The micro-Raman analysis showed that the G peak position shifted to a higher wavenumber, and the sp² bond fraction increased as the Cr concentration in the DLC films rose. The optical transmittance of the Cr-DLC films was reduced by up to 30% compared to DLC coatings due to the increased graphitization process caused by chromium addition.
- 2014 - History of diamond-like carbon filmsâFrom first experiments to worldwide applications [Crossref]
- 2014 - 60 years of DLC coatings: Historical highlights and technical review of cathodic arc processes to synthesize various DLC types, and their evolution for indus-trial applications [Crossref]
- 2023 - Doping effects on the tribological performance of diamond-like carbon coatings: A review [Crossref]
- 2022 - Diamond-like Carbon Films for Tribological Modification of Rubber [Crossref]
- 2020 - Tribomechanical properties of hard Cr-doped DLC coatings deposited by low-frequency HiPIMS [Crossref]
- 2016 - Tribology International Nanomechanical and nanotribological behavior of ultra-thin silicon-doped diamond-like carbon films [Crossref]
- 2011 - Synthesis, characterization and properties of the DLC films with low Cr concentration doping by a hybrid linear ion beam system [Crossref]