Synthesis of nanocrystalline carbon nitride films by glow discharge plasma beam deposition

Carbon nitride films were deposited on Co/Ni-covered Si(1 0 0) wafers at room temperature using a dc glow discharge plasma beam deposition method. The glow discharge has been carried out in a mixed gas of nitrogen and methane in different relative proportions and has maintained stable in an glow operating pressure around 30 Torr. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy were carried out to investigate morphology, composition, structure and crystallinity of the as-deposited films. In scanning electron microscopy images, the as-deposited films consist of crystallites with an average size of about 20–30 nm, and an interesting cauliflower structure is found in the center of a prepared sample. The X-ray diffraction results indicate that β- and graphitic-C3N4 crystallites and CNx or carbon nanotubes exist in the as-deposited films. The X-ray photoelectron spectroscopy results show that the [N]/[C] ratios are 0.34–0.46 and the peak shapes and intensities in the N 1s and C 1s regions are similar to those previously reported by our research group using the atom-beam assisted pulsed laser deposition method. The Raman spectra show two separated characteristic bands: a disordered D band (around 1323 cm−1) that indicates the presence of C3N4 components, and a graphitic G band (around 1593 cm−1). The impacts of the substrate temperatures, nitrogen/methane pressure ratios and Co/Ni layer thicknesses on the properties of the as-deposited films are discussed.