Evidence for the existence of nitrogen-substituted graphite structure by polarization dependence of near-edge x-ray-absorption fine structure

Abstract

The electronic structure of carbon nitride $({\mathrm{CN}}_{x})$ film produced by low-energy ion implantation has been studied by N 1s near-edge x-ray-absorption fine structure (NEXAFS). The NEXAFS spectra of ${\mathrm{CN}}_{x}$ film have shown three sharp ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ and one broad ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$ resonances whose intensities have clear polarization dependence. The polarization dependencies of the first and third ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ resonances have given a similar tendency to that of the ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ resonance of graphite, while the second ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ resonance has given different behavior. From the results, we concluded that the first, second, and third ${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ resonances originate from pyridinelike structure, cyanic structure, and graphitelike structure, respectively. The results show the clear experimental evidence that there exists a graphitelike structure in which some of the carbon atoms are substituted by nitrogen atoms.