Buried carbon nitride was obtained by using 100 keV N + implantation into carbon thin film with a dose of 1.2 × 10 18cm -2 at 500°C. N(1s) core level line X-ray photoelectron spectroscopy (XPS) analyses show the existence of two different N(1s) bonding states, corresponding to the nitrogen in a CN covalent bonding state and free state nitrogen, respectively. C(1s) XPS studies indicate the existence of three different C(1s) bonding states, corresponding to graphite, i-carbon and carbon with a CN covalent bonding state, respectively. Fourier transformation infrared absorption spectroscopy (FTIR) measurements point out that there is an absorption band near 2200 cm -1 assigned to the CN covalent bonding. Cross-sectional transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) measurements show that there is a buried carbon nitride layer. X-ray diffraction (XRD) shows the buried carbon nitride is amorphous. Vickers microhardness evaluation indicates the sample has a higher hardness than that of carbon thin film. The Implantation of Reactive Ions into Silicon (IRIS) computer program has been used to simulate the formation of the buried β-C 3N 4 layer as N + ions are implanted into carbon. We find good agreement between experimental measurements and IRIS simulation.