A comparison study between atomic and ionic nitrogen doped carbon films prepared by ion beam assisted cathode arc deposition at various pulse frequencies

A comparison study of microstructure and bonds composition of carbon nitride (CNx) films fabricated at atomic and ionic nitrogen source by pulse cathode arc method was presented. The relative fractions of CN/CC bonds, Nsp3C/Nsp2C and graphite-like/pyridine-like N bonding configurations in the CN films were evaluated by combining C1s and N1s X-ray photoelectron spectroscopy with the hardness and optical band gap measurement. The dependence of microstructure (quantity, size and disordering degree of Csp2 clusters) of CNx films on the nitrogen source and pulse frequency was determined by Raman spectroscopy. Films with high atomic ratio of nitrogen/carbon (0.17) and high hardness were produced at ionic nitrogen source and low pulse frequency. The results showed that ionic nitrogen source facilitated the formation of CN bonds and Nsp2C bonding configurations (mainly in graphite-like N form). Moreover presenting an optimum pulse frequency (∼10 Hz) leaded to the most nitrogen coordinated with sp3-C and the highest ratio of CN/CC bonds in the CNx films. An equilibrium action mechanism might exist between the quantity and energy of carbon and nitrogen ions/atoms, giving more nitrogen-incorporated carbon materials. These allow us to obtain the high content of NCsp3 bonding and expected bonding structure by optimizing pulse frequency and nitrogen source.