Effect of nitrogen incorporation in CNx thin films deposited by RF magnetron sputtering

Carbon nitride thin films were deposited by RF magnetron sputtering of a graphite target in a pure N2 or mixed Ar/N2 plasma. The effect of nitrogen incorporation on the growth kinetics, composition, structure and type of bonding of CNx films in a large range of N2 pressure (0.5–40 Pa) and N2 fraction in the discharge gas mixture was studied. Observations by scanning electron microscopy (SEM) of the film cross-sections revealed different morphologies depending on the N2 pressure. Transmission electron microscopy (TEM) measurements revealed that the CNx films were amorphous. By changing the deposition conditions, the N/C ratio, deduced from XPS analysis, varied from 0 to a maximum value of 0.7. Various chemical bonds for C and N atoms were found by curve fitting of N 1s and C 1s XPS peaks and by study of FTIR spectra. The optical properties of these materials were also investigated using UV-Vis-NIR absorption.