Effect of Ar:N2 ratio on structure and properties of Ni–TiN nanocomposite thin films processed by reactive RF/DC magnetron sputtering

Thin films of Ni–TiN nanocomposites have been deposited on Si (100) substrate at Ar:N2 = 1:1, 1:2 or 1:3 at ambient temperature by reactive co-sputtering of Ti and Ni targets used as RF and DC sources, respectively. X-ray diffraction (XRD) studies have shown <111> and <200> as preferred orientations for Ni and TiN, respectively. X-ray photoelectron spectroscopic examination of the films has shown Ti/N to be ≈ 1 for Ar:N2 = 1:2, and < or > 1 for Ar:N2 = 1:1 or 1:3, respectively. Scanning and transmission electron microscopic studies have shown that with an increase in Ar:N2 from 1:1 to 1:3, both porosity content and grain sizes are reduced, while the TiN volume fraction obtained by Rietveld analysis of XRD peaks is increased from 22 to 44%. The magnitude of compressive residual stress in both Ni and TiN phases is found to increase with the decrease in Ar:N2 ratio. Nanoindentation studies have shown that hardness and elastic moduli of films increase with TiN content closely following the rule of mixtures, whereas the scratch resistance scales with hardness. Furthermore, resistivity measured by Van der Pauw four-point probe method appears to be proportional to the TiN volume fraction.