SiCxNy thin films with different nitrogen contents were deposited by way of incorporation of different amounts of nitrogen into SiC0.70 using unbalanced reactive dc magnetron sputtering method. Their phase configurations, nanostructures and mechanical behaviors were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM) and microindentation methods. The result indicated SiC0.70 and all SiCxNy thin films exhibited amorphous irrespective of the nitrogen content. The phase configuration and mechanical behaviors of SiCxNy thin films strongly depended on nitrogen content. SiC0.70 exhibited a mixture consisting of SiC, Si and a small amount of C. Incorporated nitrogen, on one hand linked to Si, forming SiNx, on the other hand produced CNx and C at the expense of SiC. As a result, an amorphous mixture consisting of SiC, SiNx, C and CNx were produced. Such effects were enhanced with increase of nitrogen content. A low hardness of about 16.5 GPa was obtained at nitrogen-free SiC0.70. Incorporation of nitrogen or increase of nitrogen content increased the film hardness. A microhardness maximum of similar to 29 GPa was obtained at a nitrogen content of 15.7 at.%. This value was decreased with further increase of N content, and finally a hardness value of similar to 22 GPa was obtained at a N content of similar to 25 at.%. The residual compressive stress was consistent with the hardness in the nitrogen content range of 8.6-25.3 at.%. (C) 2009 Elsevier B.V. All rights reserved.