プラズマCVD法で形成した窒素ドープDLC膜の硬さおよび残留応力に及ぼす窒素含有率の影響

抄録

N-doped (N- ) DLC films were deposited using plasma CVD method to investigate the effects of substrate bias voltage and nitrogen flow ratio on the film structure, hardness and residual stress, which are important to apply them to machine parts. Nitrogen content in N-DLC films increased as increasing N₂ gas flow ratio, and they decreased as increasing substrate bias voltage. Results of Raman spectroscopy, I (D) / I(G) suggested that sp² clusters tended to increase as nitrogen flow ratio increased. Also, bond angles and bond lengths of the films became typical graphitic structure. And FWHM (G), which is one of the Raman parameters and indicates degree of amorphization of the films, decreased with increasing nitrogen content in the films. However, large N₂ flow rate made the structure of the film to be amorphous. FT-IR analysis suggested that relative proportion of C₂H₂ decreased because of large N₂ flow rate, and number of C-H bonds decreased in the films. Hardness of N-DLC films decreased with increasing nitrogen content of N-DLC films with varying substrate bias voltage. On the other hand, nitrogen content did not concern hardness of the films with varying nitrogen flow ratio. Comparing hardness with FWHM (G), hardness of the films increased with increase of FWHM (G) under various deposition conditions. In addition, hardness decreased with increasing Raman N/S ratio, which indicates hydrogen content in the films. Hardness and compressive residual stress related with not only nitrogen but also hydrogen content in the films.