Nanocomposite versus solid solution formation in the TiSiN system

This work contributes to the ongoing scientific debate on the structure of TiSiN coatings. In order to illuminate the formation of a nanocomposite structure versus the formation of a Ti1-xSixN solid solution, a series of TiSiN coatings was synthesized and the influence of varying N2 pressures and the addition of Ar to the deposition atmosphere on the structure of TiSiN coatings was investigated in detail. The powdered TiSiN coatings all exhibited a lower lattice parameter than reported for TiN, which further decreased with increasing N2 pressure, at comparable elemental compositions. For all coatings the presence of a crystalline Ti1-xSixN solid solution as well as an amorphous SiNx phase fraction could be detected, where more Si was incorporated into the Ti1-xSixN solid solution at higher pressures, due to less energetic growth conditions and the additional kinetic activation stemming from Ar ions resulted in less Si incorporation. Density functional theory calculations showed that defects only play a subordinate role for the low observed lattice parameters.