Growth process of hydrogenated amorphous carbon films synthesized by atmospheric pressure plasma enhanced CVD using nitrogen and helium as a dilution gas

Hydrogenated amorphous carbon films with various thicknesses were synthesized by dielectric barrier discharge-based plasma deposition under atmospheric pressure diluted with nitrogen (N₂) and helium (He) at various pulse frequencies. The C₂H₂/N₂ film showed cauliflower-like-particles that grew bigger with the increase in film's thickness. At 5 kHz, the film with a thickness of 2.7μm and smooth surface was synthesized. On the other hand, the films synthesized from C₂H₂/He had a smooth surface and was densely packed with domed particles. The domed particles extended with the increase in the film thickness, enabling it to grow successfully to 37μm with a smooth surface.