Diamond-like carbon (DLC) films were deposited on Si(100) substrates using plasma deposition technique. The deposited. films were irradiated using 2 MeV N+ ions at fluences of 1 x 10(14), 1 x 10(15) and 5 x 10(15) ions/cm(2). Samples have been characterized by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Analysis of Raman spectra shows a gradual shift of both D and G band peaks towards higher frequencies along with an increase of the intensity ratio, I(D)/I(G), with increasing ion. fluence in irradiation. These results are consistent with an increase of sp(2) bonding. XPS results also show a monotonic increase of sp(2)/sp(3) hybridization ratio with increasing ion fluence. Plan view TEM images show the formation of clusters in the irradiated DLC films. HRTEM micrographs from the samples irradiated at a fluence of 5 x 10(15) ions/cm(2) show the lattice image with an average interplanar spacing of 0.34 nm, revealing that the clusters are graphite clusters. The crystallographic planes in these clusters are somewhat distorted compared to the perfect graphite structure. (C) 2009 Published by Elsevier B. V.