| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | S.-M. Baek, Nagoya University, Japan |
| Authors: | S.-M. Baek, Nagoya University, Japan T. Shirafuji, Nagoya University, Japan S.-P. Cho, Nagoya University, Japan N. Saito, Nagoya University, Japan O. Takai, Nagoya University, Japan |
| Correspondent: | Click to Email |
Recently, diamond-like carbon (DLC) films have been performed on polymer substrates for improving scratch resistance and gas barrier properties. However, the DLC films deposited directly on polymers often encountered the problem of poor adhesion, which can reduce the performance of the DLC films. Low adhesion of the DLC films is recognized as a consequence of a residual stress due to high atomic density in comparison to polymers. Plasma pre-treatment is one of the most effective methods to modify the top surface of polymers involving surface cleaning, ablation and surface chemical functionalization. Since the bonding states of the interface are formed at the initial stage of the film growth, the adhesion strength of the films is controlled by the condition of plasma pre-treated surface. However, there have been few reports that directly dealt with the relation between the interface properties and adhesion of the DLC films.
In this study, the DLC films have been prepared on polyethylene terephthalate (PET), polycarbonate (PC) and (PMMA) substrates using a pulse biased ICP-CVD method. Plasma pre-treatments using Ar, O2, CO2, N2 and CH4 gases were performed on polymer substrates prior to DLC (non-doped, Si-doped, and oxygen-doped) coatings. The plasma pre-treated surfaces have been investigated by XPS and FT-IR ATR. The adhesion of the DLC films on polymer substrates has been characterized with a scratch test method. The scratched areas have been observed with optical microscope and SEM. Regarding the adhesion on the PET, at this moment, the doping oxygen in the films and the plasma pre-treatment have shown no effects on the adhesion of the DLC films. On the PC, on the other hand, the oxygen incorporation in the Si-doped DLC films has resulted in the enhanced adhesion of films. Furthermore, formation of the interfacial layer with N2-plasma pre-treatment has markedly increased the adhesive strength of the DLC films on the PMMA.
Since the nitrogen atoms or NH bonds are considered to be a key factor to improve the interfacial adhesion properties, we have examined formation of the Self-Assembled Monolayer (SAM) which has NH groups at the top of the SAM. The SAM is composed of a bundle of relatively long molecular chains. Thus, we can expect the SAM layer to have mechanical flexibility. This will brings about further improvement of the adhesion properties of the DLC films, such as prevention of film-peeling due to thermal history, which is now under investigation.