Mechanical and optical characteristics of superhard nanocomposite TiN/a-Si3N4 and TiCN/a-SiCN coatings produced by PECVD

There is a continuous need for new hard and superhard (H > 40 GPa) materials for applications ranging from protective coatings for cutting tools and aerospace to automobile industries, MEMS and others. In this work nanocomposite hard coatings fabricated by plasma-enhanced chemical vapor deposition from TiCl4/SiH4/CH4/N2/H2/Ar gas mixtures were found to possess unique properties such as superhardness, high toughness, and interesting optical properties and colors. The mechanical characteristics such as hardness and Young’s modulus were determined by depth-sensitive indentation. Film microstructure was studied by XRD, SEM, TEM, ERD-TOF, XPS, and AFM. Optical properties like color, refractive index and extinction coefficient were evaluated using combined spectrophotometry and spectroscopic ellipsometry. This multitechnique approach allowed us to determine the structure-property relationships. We have shown that nc-TiN/a-Si3N4 exhibits a hardness of 45 GPa, while the novel nc-TiCN/a-SiCN provides a hardness of 57 GPa in addition to a very high resistance to plastic deformation (1.8 GPa).