Carbon nitride films synthesised by magnetron sputtering at different substrate
temperatures have been studied using electron energy loss spectroscopy (EELS) during
annealing performed in situ in a transmission electron microscope (TEM). The proportion of sp2
hybridised carbon slightly decreases initially during heating, presumably because of the removal
of defects in the structure, whilst it increases at higher temperatures when graphitisation tends to
take place, as confirmed by high resolution electron microscopy (HREM). Substantial amounts
of nitrogen (up to ~ 80% ) are removed following annealing at 1000 °C. A corresponding
decrease in the pre-peak of the nitrogen spectra suggests that pyridine-like N is released by
annealing. As this peak component decreases, a second peak, of weaker intensity, is becoming
apparent in the EELS spectra when the films are heated at temperatures above approximately
700 °C. The possibility has been suggested that this corresponds to N substituted for C in a
graphitic structure, with possibly also some N2 contributing to the peak.