Influence of deposition pressure on the composition and structure of carbon nitride films deposited by direct current plasma assisted pulsed laser ablation

Carbon nitride films were deposited by pulsed laser ablation of graphite target under nitrogen atmosphere at room temperature. A direct current discharge apparatus was used to supply active nitrogen species during the deposition of carbon nitride films. FTIR and X-ray photoelectron spectroscopy (XPS) were used to characterize the composition and bonding structure of the deposited films. The influence of deposition pressure in the range 1-20Pa on the composition and bonding structure of carbon nitride films was studied. The composition and structure are strongly depended on the deposition pressure. The N/C ratio in the deposited films increases linearly with increasing deposition pressure to 10Pa, further increase of the deposition pressure results in the slight increase of N/C ratio. FTIR spectra indicate the existence of C-N, C=N and C≡N bonds in the deposited films. Increasing deposition pressure results in the increase of C=C, C=N and C≡N bonds fraction and decrease of the C-N bonds fraction in the deposited films. XPS results are consistent with FTIR results, which indicate that increasing deposition pressure leads to the increase in the fraction of N atoms bonded to sp2C atoms and the fraction of sp2C atoms bonded to N atoms, and the decrease in the fraction of N atoms bonded to sp3C atoms and the fraction of sp3C atoms bonded to N atoms.