Influence of torch power and Ar/C2H2 ratio on structure of amorphous carbon films

Abstract

The amorphous hydrogenated carbon films (a-C:H) were formed on the stainless steel substrates from an argon–acetylene gas mixture at atmospheric pressure using a direct current plasma torch discharge. The carbon films were deposited using Ar/C₂H₂ gas volume ratios 100:1, 150:1, and 200:1 and plasma torch power of 600 and 870 W. It has been obtained that the increase of the torch power leads to higher film growth rate and increases surface roughness. The growth rate varies from 20 up to 425 nm/s depending on the coating formation conditions. The structure and dominant bonds of the films were investigated by Fourier transform infrared (FTIR) and Raman spectroscopy (RS) measurements. RS results indicated that the sp²/sp³ content in the films depended on the torch power and C₂H₂ amount in argon plasma. It was demonstrated that a diamond-like / graphite-like carbon and glassy carbon films could be deposited by varying the Ar/C₂H₂ ratio and plasma torch power.
Keywords: plasma torch, carbon films, acetylene, structure
PACS: 52.75.Hn, 81.05.Uw, 68.55.-a