| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeM |
| Session: | Plasma-based Film Growth, Etching, & Processing |
| Presenter: | Yuki Hirata, Tokyo University of Science, The University of Tokyo, Japan |
| Authors: | J. Choi, The University of Tokyo, Japan Y. Hirata, Tokyo University of Science, The University of Tokyo, Japan K. Onishi, The University of of Tokyo, Japan S. Sasaki, Tokyo University of Science, Japan |
| Correspondent: | Click to Email |
Hydrogenated amorphous carbon (a-C:H) film have attracted considerable interest because of their high hardness, extremely low friction, high wear resistance, chemical inertness, and excellent gas barrier properties. These aforementioned characteristics make a-C:H films suitable for use in a wide range of applications such as tribological, anti-corrosional and gas barrier applications.
In our previous study, a-C:H film was prepared using the bipolar PBII&D technique on a trench-shaped target (20 mm pitch and 10 mm depth), and the coating uniformity was evaluated. In the bipolar PBII&D process, glow discharge plasma is generated by a positive pulse voltage applied to the target, and subsequently, a high-voltage negative pulse is applied for omnidirectional ion implantation and/or deposition to the target. However, this study revealed that the mechanical or structural properties of the a-C:H film differed greatly depending on whether the coating area was the top, sidewall, or bottom surface of the trench-shaped target. To reveal them, behavior of the ions or radicals around the trench-shaped target was analyzed through plasma simulation. Then it became apparent that these results were attribute to the nonuniformities of the incident flux or energy of the ions. Thus, in this study, non-reactive Ar gas was added to a toluene gas for deposition of a-C:H films to enhance the incident energy of the ions, and such ion-assisted effect was investigated simultaneously. The mechanical properties of the a-C:H film, including the internal stress in the thickness direction, were measured using a surface profilometer, the hardness and adhesiveness were measured using a nanoindentation hardness test and micro-scratch test, respectively. Furthermore, to evaluate the a-C:H film structure, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) were also conducted.
As a results, the uniformity of the film thickness was improved as the amount of introduced argon gas increased. Moreover, the hardness, internal stress, and adhesiveness were also improved in the case of an a-C:H film coated on a Si plate or at the top or bottom surface of a trench-shaped target. Such superior tendencies were considered to be caused by ion-assisted effects. On the other hand, in the case of the a-C:H film coated on the side wall, no improvement in film properties was seen. According to the Raman spectroscopy and FTIR, structure of a-C:H films were destroyed by Ar+ ion sputtering. That's why, it could be considered that Ar gas addition did not lead to the improvements for its properties but lead to the destruction of its structure.