Deposition and structure characterization of carbon films prepared at atmospheric pressure by plasma jet

Amorphous carbon films were deposited on stainless steel substrates by plasma jet chemical vapor deposition (PJCVD). The carbon coatings have been prepared at atmospheric pressure in an argon/acetylene mixture. The Ar/C₂H₂ gas volume ratio varied from 100:1 to 200:1, while the distance between the plasma torch nozzle exit and the samples was 0.005–0.02 m. Scanning electron microscope analysis demonstrated that the surface roughness and growth rate of the coatings increase with the decrease of the Ar/C₂H₂ ratio. The ERDA results showed that the hydrogen concentration rises from 5 at.% to 27 at.% with the increase of the distance from 0.005 to 0.02 m. The increase of the Ar/C₂H₂ ratio from 100:1 to 200:1 slightly increases the hydrogen and oxygen concentration in the films. The Raman spectroscopy results indicated that the sp³ C–C carbon sites are replaced by sp³ CH_2–3 bonds with the increase of the deposition distance. The microhardness of the carbon films deposited at 0.005 m was in range of 7.1–9.3 GPa.