Ni-toughened nc-TiN/a-SiNx nanocomposite thin films

Nanocomposite nc-TiN/a-SiNx thin films containing Ni up to ∼ 40 at.% were prepared by co-sputtering of Ti, TiNi and Si3N4 targets in Ar/N2 gas atmosphere. Adjusting TiNi/(Ti + TiNi) target power ratio altered chemical composition, microstructure and consequently mechanical properties. X-ray photoelectron spectroscopy (XPS), Grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM) and indentation were used for characterization. With increase of TiNi/(TiNi + Ti) target power ratio from 0 to 1, Ni content increased from 0 to ∼ 40 at.%. XPS results showed that there was no formation of nickel nitride. Nickel existed in a metallic state. GIXRD and TEM results confirmed that the nanocrystalline phase being solid solution of TiN with Si and Ni in its structure, or (Ti, Si, Ni)N. The matrix was amorphous silicon nitride containing metallic nickel. Nanoindentation hardness of the films remained about 30 GPa till Ni addition increases to 4.3 at.%. Toughness was estimated using microindentation method. The KIC increased from 1.15 MPa m1/2 without Ni to 2.60 MPa m1/2 with 40 at.% Ni while hardness still remained at 14 GPa.