Carbon nitride (CNX) films were prepared by nitrogen ion implantation into carbon films (a-C) deposited on Si substrates by the anodic vacuum arc. Plasma Immersion Ion Implantation (PIII) and Ion Beam (IB) implantation methods were used. X-ray Photoelectron Spectroscopy (XPS) C Is and N Is spectra of all CNX films indicate the formation of carbon-nitrogen bonds. The bonds are associated with the C 1s peaks at 286.6 eV and 285.6 eV , and the N 1s peaks at 399.1 eV and 400.6 eV. Raman spectra show that the structure of the implanted films (CNX) becomes more amorphous as the two broad peaks at 1577 cm-1 (G line) and 1350 cm-1 (D line) observed in the a-C films disappear and a broad asymmetric peak around 1500 cm-1 is formed. The interfacial tension between the a-C films and the substrate , obtained from the contact angle measurements, decreased by more than half after nitrogen implantation.