Yushi Iijima

Improvement of adhesion of hydrogen-free DLC film by employing an interlayer of tungsten carbide

Materials with poor adhesion present a problem for the application of diamond-like carbon (DLC) films. As a method for solving this problem, there is a technique that deposits an interlayer of metal between the DLC film and substrate. A tungsten carbide film (W-C film) is used as the interlayer. In this study, the effect of introducing the W-C interlayer on the adhesion of the DLC film was investigated. The W-C films were deposited using two types of cemented tungsten carbides (WCs) as the cathode, one containing Co (WC-Co) and the other containing Ti (WC-Ti), as a binder for forming the cathode shape. It is necessary to control the film thickness of the interlayer to introduce the interlayer to the DLC film. The film thickness control of W-C films became possible by using a discharge counter. DLC films were deposited using a bias voltage of -100 V. The film thicknesses of the W-C interlayer and DLC film at the time of investigating adhesion were 30 nm and 300 nm, respectively. The result of the tape-peel...

Fabrication of nitrogen-containing diamond-like carbon film by filtered arc deposition as conductive hard-coating film

Diamond-like carbon (DLC) films, which are amorphous carbon films, have been used as hard-coating films for protecting the surface of mechanical parts. Nitrogen-containing DLC (N-DLC) films are expected as conductive hard-coating materials. N-DLC films are expected in applications such as protective films for contact pins, which are used in the electrical check process of integrated circuit chips. In this study, N-DLC films are prepared using the T-shaped filtered arc deposition (T-FAD) method, and film properties are investigated. Film hardness and film density decreased when the N content increased in the films because the number of graphite structures in the DLC film increased as the N content increased. These trends are similar to the results of a previous study. The electrical resistivity of N-DLC films changed from 0.26 to 8.8 Ω cm with a change in the nanoindentation hardness from 17 to 27 GPa. The N-DLC films fabricated by the T-FAD method showed high mechanical hardness and low electrical resistivity.

Preparation of multi-layer film consisting of hydrogen-free DLC and nitrogen-containing DLC for conductive hard coating

Conductive hard-coating films have potential application as protective films for contact pins used in the electrical inspection process for integrated circuit chips. In this study, multi-layer diamond-like carbon (DLC) films were prepared as conductive hard-coating films. The multi-layer DLC films consisting of DLC and nitrogen-containing DLC (N-DLC) film were prepared using a T-shape filtered arc deposition method. Periodic DLC/N-DLC four-layer and eight-layer films had the same film thickness by changing the thickness of each layer. In the ball-on-disk test, the N-DLC mono-layer film showed the highest wear resistance; however, in the spherical polishing method, the eight-layer film showed the highest polishing resistance. The wear and polishing resistance and the aggressiveness against an opponent material of the multi-layer DLC films improved by reducing the thickness of a layer. In multi-layer films, the soft N-DLC layer between hard DLC layers is believed to function as a cushion. Thus, the tribolog...