Synthesis of Amorphous Carbon Nitride Films Using Dissociative Excitation Reaction

In this investigation, we aim to produce highly nitrogen-doped carbon, so-called carbon nitride, films without the incorporation of hydrogen. In the physical vapor deposition process, irradiation by energetic nitrogen ions increases nitrogen content without the incorporation of hydrogen. In the chemical vapor deposition process, hydrogen should be included into the film due to the use of a hydrocarbon reactant. In this study, the synthesis of carbon nitride films having high nitrogen and low hydrogen contents was attempted using a chemical-vapor-deposition apparatus. First of all, a CH₃CN+Ar mixture was selected as a reactant including hydrogen. Dehydrogenation of the reactant was carried out by plasma decomposition. Second, as a reaction system without hydrogen, BrCN+Ar was also selected for starting materials. The dissociative excitation reaction of cyanides with argon metastable atoms produces CN radicals, Ar(³P_0,2)+BrCN →Ar+Br+CN(A²Π_i, B ²Σ⁺, ⁴Σ⁺, ⁴Π). This finally proceeds to the deposition of CN radicals to form the carbon nitride film on a solid-state surface. When using the former reactant, large amounts of hydrogen remained in the amorphous carbon nitride films, although the amount of hydrogen varied with deposition conditions. The sample formed using the latter reactant was amorphous carbon nitride with very little hydrogen. The nitrogen fraction [N]/([N]+[C]) of the sample using the latter rectant is as high as ∼0.3, higher than those obtained from the samples synthesized with the former reactant.