Reported is a study of the as grown and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films deposited by a pulsed unfiltered cathodic vacuum arc process using Raman scattering, photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy. The influence of the substrate bias in as grown ta-C films and the effect of the nitrogen content in nitrogen incorporated ta-C films under a fixed bias condition were studied. The Raman spectroscopic study showed that, in the present study, the as grown ta-C films deposited at 40 V substrate bias possibly have the highest sp(3) bonded carbon concentration, as observed by the large shift in the G peak to similar to1596 cm(-1). In the case of the nitrogen incorporated ta-C films, the G peak exhibited a shift towards lower wave number with increasing nitrogen content, suggesting an increase in disorder. The PL spectra indicated a strong peak similar to2.21 eV arising due to extended defects like dislocations followed by a small one similar to1.92 eV which could be identified as a zero phonon line (ZPL) doublet. Another peak at similar to2.63 eV could be attributed to TR12 center. PL peak at similar to2.21 eV showed an inflexion in ta-C films deposited at 40 V substrate bias. An increase in intensity of the PL peak at similar to2.17 eV and its full width at half maximum (FVHM) value was also observed due to the increase in nitrogen content in the films. The FTIR spectra showed the characteristic peaks at 2958, 2366, 2350, 1610, 1512, 1047 and 710 cm-1 in as grown and nitrogen incorporated ta-C films. (C) 2004 Elsevier B.V. All rights reserved.