Cleaning of nitrogen-containing carbon contamination by atmospheric pressure plasma jet

Atmospheric pressure plasma jet (APPJ) was used to clean nitrogen-containing carbon films (C–N) fabricated by plasma-assisted chemical vapor deposition method employing the plasma surface interaction linear device at Sichuan University (SCU-PSI). The properties of the contaminated films on the surface of pristine and He-plasma pre-irradiated tungsten matrix, such as morphology, crystalline structure, element composition and chemical structure were characterized by scanning electron microscopy, grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. The experimental results revealed that the removal of C–N film with a thickness of tens of microns can be realized through APPJ cleaning regardless of the morphology of the substrates. Similar removal rates of 16.82 and 13.78 μm min^-1 were obtained for C–N films deposited on a smooth pristine W surface and rough fuzz-covered W surface, respectively. This is a remarkable improvement in comparison to the traditional cleaning method. However, slight surface oxidation was found after APPJ cleaning, but the degree of oxidation was acceptable with an oxidation depth increase of only 3.15 nm. Optical emission spectroscopy analysis and mass spectrometry analysis showed that C–N contamination was mainly removed through chemical reaction with reactive oxygen species during APPJ treatment using air as the working gas. These results make APPJ cleaning a potentially effective method for the rapid removal of C–N films from the wall surfaces of fusion devices.