Structure and properties of pulsed-laser deposited carbon nitride thin films

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 cm− 1 stretching peaks associated with CN triple bonds (CN) of nitriles and isocyanides, 1640 cm− 1 and 1545 cm− 1 associated with the CC and CN and a peak at 1730 cm− 1, which is connected to the CO carbonyls groups. Films grown at 0.66 Pa revealed the strongest CN peak.