Characterization of high-fluence nitrogen ion implanted pyrolytic graphite

We report on the preparation of carbon nitride layers with maximum nitrogen concentration of about 18 at.% by nitrogen ion implantation into pyrolytic graphite. ERDA measurements show that this low amount of nitrogen in the samples is due to the radiation-enhanced outdiffusion and desorption of nitrogen. The result of this process cannot be reduced in quantity by low temperature implantations. Following annealing the nitrogen content in the layers is lower than 2 at.%. Thus the produced carbon nitride layers are unstable at temperatures up to 1250°C. Raman and IR spectroscopy reveal that the nitrogen is either bound in pyridine-like aromatic rings or in nitrile which itself is connected to aromatic rings. The structure of the samples is amorphous.