Influence of the surface treatment of the substrate in the LCVD of CNx films

Carbon nitride (CNx) films have been prepared by UV (at 248 nm) laser-induced chemical vapor deposition using different materials (alumina, laser-activated alumina, pre-deposited Ti layers on alumina, sapphire and quartz) as deposition substrates. A mixture of ethylene. nitrous oxide and ammonia was chosen as the gas-phase precursor. The changes induced in the gas-phase composition by the irradiation in different experimental conditions were determined by IR transmission measurements. The film composition and morphology were studied by X-ray photoerectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron diffraction (TED). The degree of chemical content modification, especially its dependence on the nature of the substrate, is described for the first time. Depending on the substrate nature, the specific nucleation and growth morphology of crystallites were observed. The electron diffraction data agree well with experimental results obtained in previous works and theoretical data referring to crystalline alpha- and B-C3N4 phases. (C) 1998 Elsevier Science S.A.