Carbon nitride (CN) films were synthesized on silicon substrates by a combined ion-beam and laser-ablation method, and the variations of the structure, and the optical and the mechanical properties of the CN films were investigated as a function of ion-beam current. All the CN films were amorphous independent of the ion-beam current, and their refractive indices, extinction coefficients and optical band gaps exhibited a significant dependence on synthesis condition. In particular, the decrease of the refractive indices and the shrinkage of the optical band gap are noticeable as the ion-beam current increases. Also, the hardness of the CN films was found to decrease with ion-beam current. The observed variations of optical and mechanical properties are attributed to the changes of the atomic bonding structures which were induced by nitrogen incorporation; reduced interlinking of sp(2) clusters, increase in the number and size of sp(2) clusters, and increase of structural order in sp(2) clusters.