Abstract: Multistage trigger pulse arc source technology refers to the technology that the previous arc discharge triggers the subsequent arc discharge. It has the characteristics of working in high vacuum, instantaneous current of tens of thousands of amperes, and effective filtration of large particles, therefore, it is very suitable for the preparation of ta-C. Here, nitrogen doped ta-C films were prepared at room temperature by introducing nitrogen into the preparation process. It is found that when the vacuum pressure rises from the background vacuum to 1.3×10^-2Pa, the percentage content of N atoms in the film increases from 0% to about 8.9%, subsequently, it does not show a strict increasing relationship with the increase of nitrogen partial pressure. The doped N and C in the film react chemically to form sp² and sp³. The stress of the film decreases obviously, and the hardness also decreases, but the decrease range is small. When the deposition pressure increases from 3.7×10^-2Pa to 6.0×10^-1Pa, although the nitrogen content in the film did not increase, the content of sp² in the film gradually increased and the content of sp³ gradually decreased, which also caused the decrease of hardness and stress of the film. When the percentage of nitrogen atoms is lower than 8.9%, the friction coefficient of the films is between 0.14 and 0.15, and then increases from 0.15 to 0.5 with the increase of deposition pressure. Finally, the nitrogen-containing ta-C films were prepared on the titanium alloy substrate. In addition to the high hardness and high adhesion, the friction coefficient was 0.14-0.15, and the properties are excellent.

Key words: ta-C, nitrogen doped, residual stress, hardness, friction coefficient