H. Riascos , J. Neidhardt , G.Z. Radnóczi, J. Emmerlich , G. Zambrano , L. Hultman, P. Prieto

Carbon nitride (CNx) thin films were deposited on silicon (100) and (111) substrates at 300 -C by laser ablation of a graphite target using a pulsed Nd:YAG laser in a nitrogen atmosphere. The composition and structural properties of the films were investigated as functions of gas pressure and laser fluence. X-ray photoelectron spectroscopy (XPS) revealed a strong dependence of the amount of structurally incorporated nitrogen upon gas pressure. A maximum was observed at the highest laser fluence of 10 J/cm2 and at an intermediate pressure of 4 Pa. Further analyses of the XPS N 1s core level spectra of the CNx films, exhibiting the highest elasticity in nanoindentation experiments, revealed a typical double-peak arrangement; most pronounced for the highest laser fluence at low pressures. These two peak components indicate that the nitrogen bonded onto a graphitic structure dominates over the two-fold coordinated pyridine-like bonding configuration. This favors the growth of intersecting corrugated graphene structures that may be considered to have ‘‘fullerene-like’’ microstructures. Additionally, Fourier Transformed Infrared Spectroscopy analyses of films deposited at different pressures show the presence of 2229 and 2273 cm1 stretching peaks associated with CN triple bonds (CgN) of nitriles and isocyanides, 1640 cm1 and 1545 cm
1 associated with the CfC and CfN and a peak at 1730 cm1, which is connected to the CfO carbonyls groups. Films grown at 0.66 Pa revealed the strongest CgN peak.