Structural properties of carbon nitride films prepared by high dose nitrogen implantation into carbon thin films

Carbon nitride films were successfuly prepared by ion beam synthesis method. 100 keV N⁺ ions at a dosage of 1.2×10¹⁸ cm^-2 were implanted into carbon thin films at different temperatures. The samples were evaluated by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, cross-sectional transmission electron microscopy (XTEM), Rutherford backscattering spectroscopy (RBS), x-ray diffraction analysis (XRD), and Vickers microhardness measurement. XPS results show that most of the implanted nitrogen atoms are free state. Most of the carbon atoms have C-C bonding and a little of them form a C-N bond. It also can be clearly seen that the content of the C-N covalent bonding state in the samples is increased by raising the implanting temperature of the samples. Raman spectrum indicates that there is a Raman band near 2300 cm^-1 corresponding to carbon-nitrogen stretching. XTEM and RBS studies show that there is a buried layer of carbon nitride. XRD and TEM analyses reveal that the buried carbon nitride is predominantly amorphous with a small volume fraction of nanocrystallites. The sample has a higher hardness than that of a carbon thin film.