A-C:H Film Removal in H2 and H2/N2O Glow and Afterglow Discharge

In the experiments a stream technique has been used and it has been shown that the main product of аC:H film gasification in an afterglow region of a direct current glow discharge was methane (hydrogen discharge). A hard а-C:H film erosion rate in the afterglow region decreased exponentially with distance from an atomic hydrogen source. The disadvantage of the hydrogen discharge is low erosion yields at 320-420 K (Y ≈ 0.001 at. C/at. H, i.e., erosion rate is lower than 0.2 nm/min). For efficiency enhancement of hydrocarbon film removal in the afterglow region an H2 (40 Pa)/N2O (3-7 Pa) mixture containing oxygen component has been proposed. In such medium activated by the discharge the main erosion film products were CO and CO2. The erosion rate of the samples located at distance of 11 cm from plasma was 2 nm/min at 420 K. The addition of N2O in H2/CH4 direct current glow discharge suppressed C:H film deposition completely. The technique suggested is one of possible variants of an effective gas-discharge technology for hydrocarbon deposit removal from the remote construction parts of ITER plasma.