EELS and NEXAFS structural investigations on the effects of the nitrogen incorporation in a-CNx films deposited by r.f. magnetron sputtering

This work presents the changes induced at the nanometer scale by the nitrogen incorporation into amorphous carbon nitride a-CNx films deposited by radio-frequency (r.f.) magnetron sputtering. High N content films (20 to 33 at.%) have been analysed by electron energy loss spectroscopy (EELS) and by near edge X-ray absorption fine structure (NEXAFS). EELS spectra at C K and N K edges roughly indicate the increase of the corresponding π* features, associated to N sp2 and C sp2 bonds, vs. the N content. Fine structures of the π* region of the N K edge spectra show at least three contributions, with different evolution depending on the N content. The discrepancies between the results recorded by these two techniques are only outward and they can be explained by the influence of the plasma parameters (pressure lying from 0.5 to 13 Pa and various Ar/N2 mixtures) on the deposition process. All the results are in good agreement with the XPS analysis of the N 1s data