Crystalline carbon nitride film synthesized by ion beam assisted magnetron sputtering and thermal annealing in nitrogen gas

•Two-step process•Two strategies to promote the formation of crystalline β-C3N4 films•Some polycrystalline clusters with several nanometers can be seen in the HRTEM image.•The thermal stability film with a high probability will be recombined to N2.

Crystalline carbon nitride film has been successfully prepared by the ion beam-assist magnetron sputtering and the following thermal annealing in N2. The microstructure of the carbon nitride film is investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The film contains a very dense and homogenous distribution of crystalline grains, the lattice parameters of the crystalline phase are in good agreement with those theoretically predicted β-C3N4, and X-ray photoelectron spectroscopy (XPS) analysis also supports the existence of sp3-hybridized C–N bonds in the film. The fractional concentration of the crystalline carbon nitride particles in the film is 43.91% and the N/C ratio of the crystalline carbon nitride particles is 1.44, obviously higher than those in previous works.