The chemical composition, structural, and optical properties of nitrogenated tetrahedral amorphous carbon (ta-C:N) films deposited by a pulsed filtered vacuum arc deposition system were characterized by non-Rutherford backscattering spectroscopy, Raman spectroscopy, and ultraviolet-visible spectroscopy. It was observed that the amount of nitrogen atoms incorporated into the ta-C:N films, as well as the sp2 fraction of the films, increased with increasing nitrogen pressure PN during deposition. As a result, the optical band gap of the ta-C:N films also decreased with increasing PN. At a fixed nitrogen partial pressure of 4×10-3 Pa, the nitrogen content was found to first increase with increasing substrate negative bias voltage (-Us), up to a maximum of about 14.5 at. % at -Us of 100 and 150 V, then decreases with further increase of -Us. The sp2 fraction however increased monotonically with increasing -Us. The optical band gap of the ta-C:N films initially increased with increasing -Us, up to a maximum at a certain -Us, and then decreased with further increase in -Us. The variation of the optical band gap with the negative substrate bias voltage was discussed in terms of the different sp2-bonded carbon configurations existing in the films and the graphitization of the ta-C:N films, as indicated by the Raman and density measurement results. © 2002 American Institute of Physics.