A study of structural and mechanical properties of sputter deposited nanocomposite Ti–Si–N thin films

Abstract

Nanocomposite Ti–Si–N thin films were deposited on Si (100) and Stainless Steel (type 304) substrates by DC/RF magnetron sputtering. The effect of varying deposition parameters on the structural and mechanical properties of Ti–Si–N films was investigated by several characterization techniques such as XRD, FE-SEM, AFM, TEM, and Nanoindentor, respectively. XRD analysis of the thin films, with varying Si content revealed the (111) orientation up to 15.6 at.% Si content and thereafter the film become amorphous. The microstrain of the films decreases with increase in Si content as observed in the present work. A reduction in grain size and the transformation of pyramidal shape of grain morphology into columnar and finally to amorphous structure occurs for the films deposited, with varying Si content, as evident from the microstructural analysis. The surface roughness of the Ti-Si–N films, calculated from its AFM images, decreases with varying Si content. The hardness and Young's modulus values of Ti–Si–N films were observed to increase up to 34 GPa and 275 GPa with 15.6 at.% Si content respectively but decreases afterwards with increase in Si content. The improvement in the hardness of the films (up to 34 GPa) is due to grain boundary hardening arising from the two phase structures consisting of nanocrystallites of TiN embedded in the amorphous matrix of Si 3N 4. With increasing Si contents beyond 15 at.%, hardness of the films decreases due to incomplete nitridation of Si owing to the deficit nitrogen source during deposition of the films.