We have studied the growth and the properties of BN films prepared by exclusive deposition of mass separated 11B+ and 14N+ ions. BN films grown with ion energies of 500 eV and at substrate temperatures of 350 °C show the IR absorption peak at 1080 cm−1, characteristic for c‐BN. These films are nearly stoichiometric and, with transmission electron diffraction, the presence of c‐BN nanocrystals was revealed. We compare the growth conditions for ion beam deposition on BN, CN, and diamondlike carbon and propose that the nucleation of nanocrystalline c‐BN is related to the ionicity of the BN bond.