Yoshihiro Oka

Properties of thick DLC films prepared by plasma-based ion implantation and deposition using combined RF and H.V. pulses

Abstract A diamond-like carbon (DLC) film with a thickness of a few μm was prepared on an aluminum alloy by the hybrid process of plasma-based ion implantation and deposition using acetylene gas. The residual compressive stress of the DLC film determined from the substrate curvature decreased with increasing the negative high voltage for ion implantation and was about 0.2 GPa at the high voltage of −20 kV. Ion implantation also served to produce a graded interface between the DLC film and the substrate material. The relaxation of residual stress in the film allowed us to produce thick DLC films of high adhesion. A wear resistance test by the ball-on-disc method showed that the DLC film on an aluminum alloy substrate had the low friction coefficient of about 0.1.

Effect of Ion Implantation on DLC Preparation Using PBIID Process

This paper discusses the effects of ion implantation on a diamond-like carbon (DLC) preparation using a hybrid process of plasma-based ion implantation and deposition (PBIID) using superimposed RF and negative high-voltage pulses. Adhesion strength of a DLC film on A-5052 and SUS304 was enhanced by carbon ion implantation to substrate materials. Cross section of interface between the DLC film and substrate was observed by scanning transmission electron microscopy (STEM) and analyzed by energy dispersive X-ray spectroscopy (EDS). It was found that the amorphouslike mixing layer of graded carbon component and substrate materials was produced in the ion-implanted region of substrate and the oxide layer on the substrate surface was destroyed. Besides the reduction of residual stress in the DLC film, the formation of amorphouslike mixing layer and the destruction of oxide layer led to the enhancement in adhesion strength of the DLC film. Residual stress, sp3 fraction, hardness, density, and hydrogen content of the DLC films deposited from acetylene and toluene plasma have the variation with negative pulsed voltage for ion implantation

Enhancement of Adhesive Strength of DLC Film by Plasma-Based Ion Implantation

The thick diamond-like carbon (DLC) film of good-adhesion was prepared on a stainless steel (SUS304) substrate by a hybrid process of plasma-based ion implantation and deposition using hydrocarbon gases such as methane, acetylene, and toluene. In this process, a high repetition pulsed plasma was produced by RF pulse (13.56 MHz) with the duration of 50 µs and the repetition rate of 0.5 - 1 kHz. Besides, the plasma ions were implanted to the substrate by a negative pulsed voltage of -20 kV and the pulse duration of 5 µs. Ion implantation served to produce a graded interface of carbon component in the boundary region of DLC film and substrate, and also to reduce the residual stress to several MPa, enhancing the adhesive strength of DLC film. Furthermore, the adhesive strength of DLC film was increased above the epoxy resin strength (about 65 MPa) by implantation of mixed Si and C ions.

Hydrogen analysis in diamond-like carbon by glow discharge optical emission spectroscopy

Glow discharge-optical emission spectroscopy (GD-OES) was evaluated for hydrogen analysis in diamond-like carbon (DLC) films. DLC film samples were prepared using the plasma-based ion-implantation and deposition method (PBIID). Their hydrogen contents were determined using elastic recoil detection analysis (ERDA). The hydrogen intensity obtained by GD-OES increased gradually concomitantly with increasing hydrogen contents at the lower hydrogen content region. However, the intensity increased drastically at the higher hydrogen content region of more than about 30 at%. When the hydrogen contents increased, the correlation between GD-OES hydrogen intensity and ERDA hydrogen contents was deviated from the linear relation obtained for hydrogen-implanted silicon samples as reference materials. The sputtering rate of the DLC sample was found to vary at the high H content region. A linear relationship was obtained between the hydrogen contents and GD-OES intensities corrected with the sputtering rate of samples.

Wear Properties of DLC and Plasma Sprayed WC Structure Coating

Diamond-like carbon film (DLC) with an interlayer of plasma sprayed tungsten-carbide (WC) was prepared on an aluminum alloy substrate (A5052) by a hybrid process of plasma-based ion implantation and deposition using hydrocarbon gas. Typical thicknesses of DLC and WC films were 1 μm and 100 μm, respectively. The hardness and friction coefficient of DLC were typically 15 GPa and 0.15, respectively. The durability of DLC/WC/A5052 system was evaluated from the measurement of the friction coefficient by a ball-on-disk friction tester in which the loaded ball was drawn repeatedly across a sample and the load was increased with each traverse. For the DLC/A5052 system, which has no WC interlayer, the DLC film was broken quickly because of distortion of the substrate. For the DLC/WC/A5052 system, on the other hand, the DLC film was excellent in durability for long running. The wear rate of rubber rotor to the metal rotor was measured by a roller-pitching-type wear testing machine, showing large reduction in wear rate using DLC-coated metal rotor.

Microstructural Observation of Diamond Like Carbon Film Prepared from C2H2 / C5H6CH3 Plasma Beam Source

In this study, the microstructure of two kinds of diamond-like carbon films was studied. These films were produced during the deposition of two kinds of hydrocarbon gas plasma by a newly developed technique called plasma based ion implantation (PBII). Microstructural analysis was performed by means of high resolution transmission electron microscopy (HRTEM). An amorphous DLC film was obtained by using C2H2 plasma. The crystal structure of carbon ( (C 168H ) was generated inside the DLC film when C5H6CH3 plasma was used. The effect of the precursor gases used in the present experiment on the microstructure of the DLC film was also studied.