Hardness and surface roughness of hydrogenated amorphous carbon-based films synthesized by atmospheric pressure-plasma enhanced chemical vapor deposition at low temperature

Hydrogenated amorphous carbon (a-C:H)-based films were synthesized by the dielectric barrier discharge-based plasma deposition at atmospheric pressure from C₂H₂ diluted with He or N₂ gas with varying dilution ratios (R) and their hardness, surface roughness and chemical composition were analyzed. The films deposited from C₂H ₂/N₂ contained nitrogen elements and they were softer with rougher surface compared with the a-C:H films deposited from C ₂H₂/He. Additionally the amount of nitrogen incorporation increased as the ratio R decreased, which led to deterioration of hardness and surface smoothness. As for C₂H₂/He, the film hardness slightly increased by decreasing the ratio R and the a-C:H (R = 1%) showed a maximum hardness of 1.1 GPa.