On the structure and composition of polycrystalline carbon nitride films synthesized by reactive rf magnetron sputtering

Polycrystalline β-C3N4 films have been deposited on single-crystal KCl(100) substrates using reactive rf magnetron sputtering. The films have been characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. A large number of grains are found distributed in various regions of the film. The dimension of the largest grain is about 4 μm. The film is composed mainly of C and N with a small amount of O. XPS data show N-bonded to sp3-hybridized C with some surface oxidation. The N/C ratio in the β-C3N4 region is deduced to be 1.23–1.27, close to an expected stoichiometric value of 1.33. The TED-measured interplanar spacings suggest that the crystalline grains are hexagonal with lattice parameters of a=6.30 Å and c=2.46 Å.