Structure of nitrogenated amorphous carbon films from NEXAFS

The change in the structure of tetrahedral amorphous carbon (ta-C) films by nitrogen incorporation is studied by near-edge Xray absorption fine structure (NEXAFS) spectroscopy and electron energy-loss spectroscopy (EELS). NEXAFS spectroscopy can be used to determine the molecular structure of amorphous nitrogenated carbon (a-CNx) films due to its superior energy resolution as compared to EELS. This shows the structure of the films to be close to pyridine. The N K-edge spectra obtained from these spectroscopic techniques are decomposed into several peaks in order to compare the film structure after nitrogen incorporation. A comparative and combined study of NEXAFS spectroscopy and EELS reveals that as the nitrogen concentration in the films increases, the peaks pi* and sigma* at the C K-edge move towards higher energy and the pi*/sigma* intensity ratio at both edges decreases. These results indicate that there is an increase in the concentration of C=C and C=N relative to C-C and C-N bonds with nitrogen concentration, respectively. The difficulty of nitrogen doping of ta-C is also interpreted from the ratio of pi* and sigma* at C and N K-edges. (C) 2002 Elsevier Science B.V All tights reserved.