MICROSTRUCTURAL CHARACTERIZATION OF CARBON-FILMS AND CNX FILMS PRODUCED BY N+ IMPLANTATION

We report on a study of the electronic, chemical and lattice structure of carbon films and of the microstructural modifications induced by N + implantation. Correlations were made with the new mechanical propert ies of the implanted films. The C films were r.f. magnetron sputtered from a graphite target with Ar discharge. N+ implantations were perfor med with energies ranging from 30 to 160 keV and at a fluence of 2 x 1 0(17) N+ cm(-2). The effects of N on the structural and chemical prope rties of the C films were studied by means of x-ray photoelectron spec troscopy (XPS) and Raman scattering. Nuclear reaction analysis (NRA) a nd elastic recoil detection (ERD) were used to determine the atomic co mposition and density of the films. The carbon films consisted of two phases: microcrystalline graphitic domains dispersed in an amorphous m atrix. The ratio of the hardness to the Young modulus, H/E, is compara ble to that of diamond. N+ implantation produces new bondings in these films, enhances the amorphicity and increases the disorder of the gra phitic phase. The diamond-like features of the electronic valence band (strong s-p-orbital mixing) are preserved in the implanted films, tog ether with the Young modulus of the network. Only the top of the valen ce band was affected by the ion irradiation. The new microstructure of the surface region of the implanted films resulted in an improved fri ction behaviour. N+ implantation decreased the ratio H/E to a value si milar to that of metallic hard coatings.