A study on interfacial phase of Ti-Si-N composite films

To reveal the interfacial phase structure and its effect on mechanical properties of Ti-Si-N composite films, x-ray diffractometry, high-resolution transmission electron microscopy, Auger electron spectroscopy, and microhardness tester were employed to investigate the interfacial phase structure and mechanical properties of magnetron sputtered Ti-Si-N composite films. A series of TiN/Si3N4 multilayered films in nanometer scale were also prepared and characterized for comparison. The results indicated that Ti-Si-N composite films formed a structure of nanocrystalline TiN surrounded by Si3N4 interfacial phase. In the Ti-Si-N composite film with lower silicon content, the Si3N4 interfacial phase with a thickness of less than 1 nm crystallized and formed a coherent interface with TiN nanocrystals, leading to an enhancement in the hardness of the film. Whereas, in the composite film of larger silicon content, Si3N4 phase existed as amorphous and resulted in a decrease in hardness. Our research indicated that the crystallization of Si3N4 interfacial phase was essential to obtain a high hardness in the Ti-Si-N composite films, and the strengthening mechanism of the composite films appeared to be the same as TiN/Si3N4 multilayered films.