Abstract Thin ( d ⩽ 10 nm) films of almost stoichiometric silicon nitride were prepared by implanting nitrogen ions with energies below 5 keV into silicon with subsequent thermal annealing. A combination of Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS) was used to determine the chemical composition and to investigate the chemical bonding states of the thin films. The spectra are in good agreement with those obtained for Si 3N 4 produced by chemical vapour deposition. The use of AES and electron ELS allowed the stepwise formation of the SiN bonds to be investigated for the first time, and hence further information about the electronic structure of Si 3N 4 was obtained. Depth-concentration profiles for nitrogen are presented.