Monitoring the structural and chemical properties of CNx thin films duringin situ annealing in a TEM

Carbon nitride films synthesised by magnetron sputtering at different subst rate temperatures have been studied using electron energy loss spectroscopy (EELS) during annealing performed in situ in a transmission electron micro scope (TEM). The proportion of sp(2) hybridised carbon slightly decreases i nitially during heating, presumably because of the removal of defects in th e 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 similar to 80%) are removed f ollowing annealing at 1000 degreesC. A corresponding decrease in the pre-pe ak of the nitrogen spectra suggests that pyridine-like N is released by ann ealing. As this peak component decreases, a second peak, of weaker intensit y, is becoming apparent in the EELS spectra when the films are heated at te mperatures above approximately 700 degreesC. The possibility has been sugge sted that this corresponds to N substituted for C in a graphitic structure, with possibly also some N-2 contributing to the peak.