Carbon nitride films have been generated on Si(100) substrates by low-energy plasma beam deposition with a mixed N-2(+)-N+/Ne+-beam at an ion energy of 120 eV. The nitrogen concentration in the CNx-films, measured by MCs+-mass spectrometry, varies between 25 and 41 at%. From an analysis of the C1s and N1s XPS-peak structures, two C-N binding configurations in the CNx-layers were identified. One phase has C3N4-stoichiomeuy and is referred to as a beta-C3N4-like phase. The other configuration with x between 0.2 and 0.8 is identified as a carbon-rich sp(2)-bonded structure. The results are compared with CNx-films which were previously deposited with N+/N-2(+)-Ar+-plasma beams. A strong correlation of the N+/N-2(+)-ratio in the plasma beam with the: binding configuration and the optical band gap was found. For a maximum N+/N-2(+)-ratio the tetrahedraily bonded component of the films and the optical band gap achieve their highest values. Transmission electron diffraction displays three diffuse diffraction rings which can be matched with the calculated lattice structure of the beta-C3N4 phase.