AN X-RAY PHOTOELECTRON-SPECTROSCOPY STUDY OF CARBON NITRIDE FILMS GROWN BY LOW-ENERGY ION-IMPLANTATION

Nitrided carbon surface coatings with [N]/[C] ratios in the range 0.05 -0.34 were prepared by nitrogen ion implantation with energies ranging between 250 and 5000 eV on graphite and hydrogenated amorphous carbon . We present a core-level X-ray photoemission spectroscopy study of th e composition and chemical bonding in these materials. The composition s with higher N concentrations were obtained by consecutive implanting from higher to lower energies. The N Is line shape shows the contribu tion of at least four main chemical species: (i) nitrile at 398.70 eV; (ii) at 399.70 eV, metastable, associated with high energy ion bombar ding, could be strict nitride bonding; (iii) imine type at 400.7 eV of N incorporated into the hexagonal rings of the graphitic structure; ( iv) surface-absorbed molecular nitrogen, at 402.4 eV. Their relative s tabilities were also studied. On the contrary, the C Is line shape did not show resolved peaks but a gradual broadening and a shift of its c entroid, increasing linearly with increasing nitrogen concentration. T he shifts observed were relatively large for these materials of very l ow ionicity. The electron energy loss structures associated with the C Is peak indicates an important reduction in valence pi electrons scre ening with increasing nitrogen concentration, thus making a contributi on to those shifts.