Modified π-states in ion-irradiated carbon

CVD polycrystalline diamond film, pulse laser-deposited (PLD) carbon film and highly oriented pirolitical graphite (HOPG) as reference, were modified by means of Ar+ ion bombardment and characterized by means of Raman scattering, transmission electron microscopy, electron-diffraction (TEM), reflected electron energy loss specroscopy (REELS) and X-ray photoelectron spectroscopy (XPS) techniques. It was found that the diamond was transferred to a carbon with halo-like morphology and disordered stack of graphene segments. Instead of the well-known electron energy loss peak of graphite at 6.5 eV, a new REELS peak appeared at 4-5 eV energies. The observed effect was explained by the modification of π-system in carbon films as a consequence of the formation of non-planar, nanometer-sized graphitic planes.