Influence of deposition conditions on the microstructure and mechanical properties of Ti-Si-N films by DC reactive magnetron sputtering

Ti-Si-N films were codeposited onto SKD 11 steel substrates using a DC magnetron sputtering technique with separate Ti and Si targets. High resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) revealed that the microstructure of the Ti-Si-N films was characterized by a nanocomposite consisting of nano-sized TiN crystallites surrounded by an amorphous Si3N4. The highest hardness value of approximately 38 GPa was obtained at a Si content of ∼11 at.%, where the microstructure had fine TiN crystallites (approximately 5 nm in size) dispersed uniformly in an amorphous matrix. As the Si content in Ti-Si-N films increased, the TiN crystallites of initially aligned microstructure became randomly oriented, finer, and fully penetrated by the amorphous phase. Free Si appeared in the films due to the deficit of the nitrogen source as the Si content increased. A thickening of the amorphous Si3N4 phase by increasing the Si content resulted in a reduction of hardness when the Si content increased beyond a critical point