Near edge x-ray absorption fine structure of thermally annealed amorphous nitrogenated carbon films

The change of structure of tetrahedral amorphous carbon (ta-C) films after nitrogen incorporation, particularly at a high concentration, was studied by near edge x-ray absorption fine structure (NEXAFS) spectroscopy and it was found to be very close to pyridine. The pi* peak at the N K (nitrogen K) edge was decomposed into three components corresponding to different resonances. From a detailed analysis of N K edge by NEXAFS spectroscopy it was revealed that as the nitrogen concentration in the films increases, the sigma*/pi* intensity ratio decreases, indicating that there is an increase of the amount of C=N relative to the C-N bonds. By thermal annealing at different temperatures, up to 800 degrees C, the nitrogen concentration in the films is reduced. Intensity as well as the position of the pi* peak at the C K edge changed with annealing temperature. At the same time, a decrease of the intensity of the pi* peak at the N K edge and a very interesting change of the relative intensities of the three split components of this pi* peak have been observed. The possible changes of structure of nitrogenated carbon films by annealing and thermal stability of the films have been thoroughly emphasized. (C) 2000 American Institute of Physics. [S0021-8979(00)09422-6].