Carbon nitride (CN(x)) and amorphous carbon (a-C) thin films are deposited by reactive magnetron sputtering onto silicon (001) wafers under controlled conditions to achieve amorphous, graphitic and fullerene-like microstructures. As-deposited films are analyzed by Spectroscopic Ellipsometry in the UV-VIS-NIR and IR spectral ranges in order to get further insight into the bonding structure of the material. Additional characterization is performed by High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Between eight and eleven resonances are observed and modeled in the ellipsometrically determined optical spectra of the films. The largest or the second largest resonance for all films is a feature associated with C-N or C-C modes. This feature is generally associated with sp(3) C-N or sp(3) C-C bonds, which for the nitrogen-containing films instead should be identified as a three-fold or twofold sp(2) hybridization of N, either substituted in a graphite site or in a pyridine-like configuration, respectively. The pi ->pi* electronic transition associated with sp(2) C bonds in carbon films and with sp(2) N bonds (as N bonded in pyridine-like manner) in CN(x) films is also present, but not: as strong. Another feature present in all CN(x) films is a resonance associated with nitrile often observed in carbon nitrides. Additional resonances are identified and discussed and moreover, several new, unidentified resonances are observed in the ellipsometric spectra. (C) 2009 Elsevier B.V. All rights reserved.