Carbon nitride films are deposited on Si(001) substrates by reactive d.c. magnetron sputtering graphite in a pure N2 discharge. The chemical bonding and structure of carbon nitride films were probed using Fourier transformation infrared (FTIR) and near edge X-ray absorption fine structure (NEXAFS), and the hardness was evaluated using nanoindentation experiments. The structure and hardness for the films are dependent on the substrate temperature (T(s)). FTIR and NEXAFS spectra show that N atoms are bound to sp1, sp2 and sp3 hybridized C atoms, and the intensity of p(*) resonance for C1s NEXAFS spectra is the lowest for the film grown at T(s) = 350°C, having a turbostratic-like structure, high hardness and stress. The correlation between the structure and hardness of carbon nitride films is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.Carbon nitride films are deposited on Si(001) substrates by reactive d.c. magnetron sputtering graphite in a pure N2 discharge. The chemical bonding and structure of carbon nitride films were probed using Fourier transformation infrared (FTIR) and near edge X-ray absorption fine structure (NEXAFS), and the hardness was evaluated using nanoindentation experiments. The structure and hardness for the films are dependent on the substrate temperature (Ts). FTIR and NEXAFS spectra show that N atoms are bound to sp1, sp2 and sp3 hybridized C atoms, and the intensity of p* resonance for C1s NEXAFS spectra is the lowest for the film grown at Ts = 350°C, having a turbostratic-like structure, high hardness and stress. The correlation between the structure and hardness of carbon nitride films is discussed.