CARBON NITRIDE FORMATION BY LOW-ENERGY NITROGEN IMPLANTATION INTO GRAPHITE

Recently, some attempts to produce the new beta-C3N4 phase with hardne ss higher than diamond have been reported. In this paper, a model stud y of carbon nitride formation by low-energy nitrogen implantation into graphite is presented. Room temperature (RT) and hot (500 degrees C) nitrogen implantations were performed at saturation and low doses. The formation of chemical bonds between implanted nitrogen and carbon ato ms was assessed by in situ X-ray photoelectron spectroscopy. It was fo und that two dominant nitrogen bonding states are formed in the implan ted layer. The relative distribution of these states depends on the im plantation temperature, dose and post-annealing process. Hot nitrogen implantation results in a predominant population of the more covalent (higher binding energy) nitrogen bonding state which has been suggeste d to be characteristic of the beta-C3N4 phase. Post-annealing of a low -dose nitrogen-implanted graphite results in a distribution of the nit rogen bonding states similar to the hot implantation case. RT implanta tion at saturation doses followed by annealing leads to a different di stribution of the nitrogen bonding states. The implantation-induced da mage was investigated by means of electron-excited C(KVV) Auger line s hape measurements. Hot implantation results in point defect formation, although the graphite structure is not completely amorphized. The exp erimental results suggest that hot nitrogen ion beam-assisted depositi on can lead to the formation of the new beta-C3N4 phase.