On the Mechanism of Nitrogenated Carbon Film Deposition by PACVD in the Presence of Nitrogen. A Cryo‐Trapping Assisted Mass Spectrometric Study

Abstract

AbstractThe well‐documented effect of film inhibition/perturbation that nitrogen molecules have in the plasma‐assisted (PA)CVD of a‐C/N:H films in a DC glow discharge reactor under low pressure is investigated. Plasma parameters, gas‐phase composition, and film characteristics are recorded using several diagnostic techniques, including the newly developed cryo‐trapping assisted mass spectrometry (CTAMS). Five gas mixtures are investigated; CH4/H2, CH4/N2/H2, and CH4/Ar/H2 as precursors for the films, at low relative concentration of the hydrocarbon molecule (methane), and H2/N2 and He/N2 as film etchers. There are found to be strong differences in the composition of reaction product between systems in which plasma/surface interactions are dominated by ion‐induced processes (sputtering), and those where chemical reactions with nitrogenated species would behave as scavengers of the film precursor. The implications of these findings for the proposed mechanisms of a‐C/N:H film growth are addressed. The application of the scavenger technique for the inhibition of tritium‐containing carbon co‐deposits in the divertor region of fusion reactors, as an international thermonuclear experimental reactor (ITER) in the carbon‐dominated scenarios, is analyzed in the light of these findings.