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 degrees 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/cm(2) 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 (C N) of nitriles and isocyanides, 1640 cm(-1) and 1545 cm(-1) associated with the C=C and C=N and a peak at 1730 cm(-1,) which is connected to the C=O carbonyls groups. Films grown at 0.66 Pa revealed the strongest C N peak. (c) 2005 Elsevier B.V. All rights reserved.