Effect of nitrogen content on phase configuration, nanostructure and mechanical behaviors in magnetron sputtered SiC xN y thin films

Abstract

SiC x N y thin films with different nitrogen contents were deposited by way of incorporation of different amounts of nitrogen into SiC 0.70 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 SiC 0.70 and all SiC x N y thin films exhibited amorphous irrespective of the nitrogen content. The phase configuration and mechanical behaviors of SiC x N y thin films strongly depended on nitrogen content. SiC 0.70 exhibited a mixture consisting of SiC, Si and a small amount of C. Incorporated nitrogen, on one hand linked to Si, forming SiN x , on the other hand produced CN x and C at the expense of SiC. As a result, an amorphous mixture consisting of SiC, SiN x , C and CN x were produced. Such effects were enhanced with increase of nitrogen content. A low hardness of about 16.5 GPa was obtained at nitrogen-free SiC 0.70. Incorporation of nitrogen or increase of nitrogen content increased the film hardness. A microhardness maximum of ∼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 ∼22 GPa was obtained at a N content of ∼25 at.%. The residual compressive stress was consistent with the hardness in the nitrogen content range of 8.6–25.3 at.%.