Role of Nitrogen in the Formation of HC—N Films by CH4/N2 Barrier Discharge Plasma: Aliphatic Tendency

We have studied the influence of nitrogen on the chemical properties of the hydrogenated carbon nitride (a-CNx:H) film deposited by CH4/N2 dielectric barrier discharge (DBD) plasma. X-ray photoelectron spectroscopy (XPS) indicates that carbon and nitrogen form an unpolarized covalent bond in these CsNx materials, and the observed chemical shift in the C 1s and N 1s binding energy is explained with respect to N 1s incorporation. Furthermore, the average nitrogen content (N/C ≈ 0.76) in the films was systematically varied by changing the nitrogen partial pressure (CH4/N2 ≈ from 5:1 to 1:7) which is well supported by the elemental analysis. Fourier transform infrared (FTIR) absorption spectra exhibit significant changes in different CsN, CtN, and NH/OH molecular bands at higher nitrogen concentration in the film. The isonitrile and nitrile groups (sNC and sCN) are increased with the increase of deposition time. In addition, the elemental analysis, proton NMR, and thermolysis mass spectrum show that the composition of the film with the ratio CH4/N2 ≈ 1:1 is C, 67.68; H, 9.88; N, 16.53 (in wt %) and that the film is composed of polymers, probably containing linear chains which are cleaved off on heating in vacuum.