The structure of amorphous carbon nitride films using a combined study of NEXAFS, XPS and Raman spectroscopies

The nature of bonding in tetrahedral amorphous carbon nitride (ta-C:N) films deposited by filtered cathodic vacuum arc (FCVA) technique was studied with near edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron and Raman spectroscopies. The interpretation and interrelation of these spectra are discussed. The changes in the local structure were systematically studied as a function of nitrogen content. Deconvolution of the C 1s and N 1s XPS spectra shows that the sp3-C fraction decreases with an increase in nitrogen content. The π* peak at the C K (carbon K) and at the N K (nitrogen K) edges were systematically studied. Comparison of intensities of the π* peak confirms the formation of CN bond at the expense of CC bond. Analysis of NEXAFS spectra at N K edge revealed as the nitrogen concentration in the films increases, the π*/σ* intensity ratio increases, indicating that there is an increase of the amount of CN bond relative to the C-N bonds. Raman parameters, such as G peak width, ID/IG ratio, skewness of the G line (Q), were critically analysed in terms of N content and sp2 content of the films. We demonstrate that the combined study of normalised Raman, XPS and NEXAFS spectra is very useful in determining the role of nitrogen incorporation in the structure of ta-C films. The hardness values, measured by nanoindentation technique reduced at higher (>7 at.%) N content films.