Carbon nitride (C1-xNx) thin films were deposited at room temperature on Si and Ge substrates by the reactive ion beam sputter deposition (IBSD) technique. A pure graphite target has been sputtered with a nitrogen ion beam extracted from a Kaufman-type ion source. The films were characterized by Raman spectroscopy, IR absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). There was no clear indication of the presence of C-N single bonds in the films. Raman and IR absorption spectra show two characteristic bands; a broad band composed of graphite G-band and disordered D-band of carbon, and the other associated with C=N triple bonds. The D-band suggests the presence of an amorphous carbon network, The XPS spectra show the presence of C=N triple and C=N conjugated double bonds. As a reliable structural model of the C1-xNx films, an amorphous network with C=N triple bond terminations, as well as substitutions of nitrogen into the network, have been proposed. Reactive IBSD with high acceleration energy and/or the irradiation of the primary ions onto the substrate have been found to be important to form a sp(3)-rich amorphous C-N network.