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 b y near edge x-ray absorption fine structure (NEXAFS) spectroscopy and it wa s 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 resona nces. From a detailed analysis of N K edge by NEXAFS spectroscopy it was re vealed that as the nitrogen concentration in the films increases, the sigma */pi* intensity ratio decreases, indicating that there is an increase of th e amount of C=N relative to the C-N bonds. By thermal annealing at differen t temperatures, up to 800 degrees C, the nitrogen concentration in the film s 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 th e intensity of the pi* peak at the N K edge and a very interesting change o f the relative intensities of the three split components of this pi* peak h ave 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 ].