Formation of Diamond-Like Carbon Film on Organic Substrate by High Power Impulse Magnetron Sputtering
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Journal of The Surface Finishing Society of Japan |
| Authors | Takayuki Ohta, Rikuto OGUSHI, Akinori Oda, Hiroyuki Kousaka |
| Institutions | Gifu University, Meijo University |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled āExecutive SummaryāThis research investigates the deposition of hard Diamond-Like Carbon (DLC) films onto insulating organic substrates using High Power Impulse Magnetron Sputtering (HiPIMS) without requiring a complex radio-frequency (RF) substrate bias.
- Core Achievement: Successful deposition of DLC films (~200 nm thick) on Polyacetal (POM), Polytetrafluoroethylene (PTFE), and Polyamide 6 (PA6) substrates using a grounded (0 V bias) holder.
- Material Performance: DLC films on PA6 and PTFE exhibited high sp3 bonding ratios (20.9% and 20.4%, respectively), indicating the formation of hard, high-quality coatings suitable for tribological applications.
- Process Advantage: HiPIMS eliminates the need for RF biasing, simplifying the coating process for insulating polymer components and reducing potential thermal damage.
- Plasma Dynamics: HiPIMS generated C+ ion fluxes approximately 100 times greater than standard Direct Current Magnetron Sputtering (DCMS) under comparable average power.
- High-Energy Ions: Energy-resolved mass spectrometry confirmed the presence of high-energy C+ ions (up to 40 eV), which are critical for achieving high sp3 content via sub-surface implantation.
- Mechanism Insight: The C+ ion energy distribution followed a Maxwellian distribution, suggesting that C+ generation is dominated by plasma reactions (e.g., charge exchange with Ar+) rather than direct sputtering.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Material | Carbon (2 inch) | - | HiPIMS source |
| Pulse Width (Ton) | 8 | Āµs | HiPIMS operation |
| Pulse Frequency | 400 | Hz | HiPIMS operation |
| Duty Cycle | 0.32 | % | (8 Āµs ON / 2500 Āµs period) |
| Peak Target Current | 75 | A | Instantaneous HiPIMS peak |
| Peak Power Density | 1.7 | kW/cm2 | Instantaneous power density |
| Process Pressure | 0.5 | Pa | Argon atmosphere |
| Ar Gas Flow | 4 | sccm | - |
| Film Thickness | ~200 | nm | DLC layer after 5 hours |
| Substrate Bias | 0 | V | Substrate holder grounded |
| C+ Ion Peak Energy | ~5 | eV | Measured IEDF peak |
| C+ Ion Energy Tail | >40 | eV | High-energy component observed |
| C+ Flux (HiPIMS vs DCMS) | ~100 | times greater | HiPIMS relative to DCMS maximum flux |
| sp3 Content (PA6) | 20.9 | % | Determined by XPS C1s analysis |
| sp3 Content (PTFE) | 20.4 | % | Determined by XPS C1s analysis |
| sp3 Content (POM) | 13.7 | % | Determined by XPS C1s analysis |
| Raman Excitation Wavelength | 514.5 | nm | Ar ion laser |
Key Methodologies
Section titled āKey Methodologiesā- Deposition Setup: A HiPIMS system was used with a 2-inch carbon target. Substrates (POM, PA6, PTFE) were placed 84 mm from the target on a grounded, water-cooled holder.
- Process Environment: The chamber was evacuated to 1.0 x 10-3 Pa, then filled with Argon gas (4 sccm) to maintain a process pressure of 0.5 Pa.
- HiPIMS Recipe: A voltage pulse (8 Āµs width, 400 Hz frequency) was applied to the target, generating a peak current of 75 A and a peak power density of 1.7 kW/cm2. Deposition time was 5 hours.
- Structural Characterization:
- Raman Spectroscopy: Used to analyze the structure, focusing on the D-peak (~1350 cm-1, sp2 defects) and G-peak (~1550 cm-1, sp2 ring stretching) to assess film quality (ID/IG ratio and G-peak FWHM).
- XPS (X-ray Photoelectron Spectroscopy): Used to quantify the chemical bonding state (sp3/sp2 ratio) by deconvoluting the C1s orbital signal (sp2 at 284.2 eV, sp3 at 285.3 eV).
- Plasma Characterization:
- Energy-Resolved Mass Spectrometry (EQP300): Used to measure the Ion Energy Distribution Functions (IEDFs) for C+ and Ar+ ions at the substrate position.
- Data Acquisition: Measurements were time-integrated over one full pulse cycle (ON time + OFF time) to capture the total ion flux incident on the substrate.
Commercial Applications
Section titled āCommercial ApplicationsāThe ability to deposit hard, low-friction DLC coatings onto lightweight, insulating polymers without thermal damage or complex RF biasing opens up significant opportunities in mechanical and automotive engineering.
- Automotive and Transportation: Coating sliding components (gears, bearings, bushings) in Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) to reduce friction loss and improve energy efficiency.
- Tribological Systems: Enhancing the wear resistance and lowering the coefficient of friction of polymer-based mechanical parts (e.g., PA6, PTFE) used in precision machinery.
- Lightweighting: Facilitating the replacement of heavier metal components with coated, high-performance plastics, contributing to overall system weight reduction.
- Insulating Component Protection: Applying protective, hard coatings to complex polymer geometries where traditional plasma processes requiring high substrate bias are impractical or damaging.
- Consumer Electronics: Coating plastic moving parts where durability and smooth operation are required without adding significant mass.
View Original Abstract
Diamond-like carbonļ¼DLCļ¼film was deposited on organic substrates using highpower impulse magnetron sputteringļ¼HiPIMSļ¼without substrate bias voltage. The DLC film properties were evaluated using Raman spectroscopy and X-ray photoelectron spectroscopy. Results show that the sp3 contents of the DLC films on PTFE or PA6 substrates were greater than those on POM substrate. The ion energy distribution functionsļ¼IEDFsļ¼of carbon ion and argon ion were measured using energy-resolved mass spectrometry to evaluate high-energy ion production. From HiPIMS, high-energy carbon ion with more than 30 eV was detected, whereas argon ions were distributed in the low-energy region. Comparison of the IEDFs of carbon and argon ions in HiPIMS to those obtained using direct current magnetron sputtering confirmed that higher-energy carbon ions, which contribute to increased sp3 bonding, were produced with higher intensity in HiPIMS.