The location and effects of Si in (Ti_1–xSi_x)N_y thin films

(Ti_1–xSi_x)N_y (0 ≤ x ≤ 0.20; 0.99 ≤ y(x) ≤ 1.13) thin films deposited by arc evaporation have been investigated by analytical transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and nanoindentation. Films with x ≤ 0.09 are single-phase cubic (Ti,Si)N solid solutions with a dense columnar microstructure. Films with x > 0.09 have a featherlike microstructure consisting of cubic TiN:Si nanocrystallite bundles separated by metastable SiN_z with coherent-to-semicoherent interfaces and a dislocation density of as much as 10¹⁴ cm⁻² is present. The films exhibit retained composition and hardness between 31 and 42 GPa in annealing experiments to 1000 °C due to segregation of SiN_z to the grain boundaries. During annealing at 1100–1200 °C, this tissue phase thickens and transforms to amorphous SiN_z. At the same time, Si and N diffuse out of the films via the grain boundaries and TiN recrystallize.