CNx/TiN multilayer films with different bilayer periods were produced by reactive unbalanced magnetron sputtering. Low-angle X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM) were employed to investigate the structural properties of these films including layer density, bilayer thickness, layer thickness variation, and interface roughness. The results showed that the density of TiN layers in different CNx/TiN multilayers ranged from similar to 4.3 x 10(3) to 4.9 x 10(3) kg/m(3) with the CNx density being around 2.1 x 10(3) 2.3 x 10(3) kg/m(3). The bilayer thicknesses of those multilayers are about, respectively, 2.2, 5.0, and 10.2 nm, with a variation of layer thickness being similar to 0.2-0.3 nm for both TiN and CNx layers due to the random characteristic of particle deposition. Analysis also revealed that for the multilayer with 5-nm-thick bilayer an initial system instability caused the bilayer thicknesses in the early growth time (similar to 4.6 nm) to be less than those at the later stage of growth (similar to 5 nm). By incorporating three different interface roughness models into low-angle X-ray diffraction simulations, it was found the underlying interface roughness of CNx/TiN multilayers increased with the bilayer number, and the roughness of three different multilayers was determined to be, respectively, about 1.1, 1.5, and 2.1 nm, showing an increasing trend with the bilayer thickness. (c) 2004 Elsevier B.V. All rights reserved.