Influence of acetylene to argon flow rate ratios on structure and properties of hydrogenated amorphous carbon films produced on steel substrates by plasma immersion ion implantation and deposition

Hydrogenated amorphous carbon (a-C:H) films were fabricated using mixed acetylene and argon plasma with various flow rate ratios of acetylene to argon. Raman scattering and x-ray photoelectron spectroscopy show that changing the flow rate ratios (F_C2H2 to F_Ar) has a large impact on the structure of the films. Enhanced film hardness and reduced surface roughness were achieved at higher ratios attributable to the high ion flux and efficient etching by hydrogen. However, the film surface exposed to atomic hydrogen at a higher C₂H₂ flow rate becomes rougher. The sp³ content and film hardness also reach saturation combined with a fissile surface due to the high stress. © 2007 Materials Research Society.