Nanoindentation measurements on modified diamond-like carbon thin films

• Stress reduction in DLC due to introduction of nitrogen, copper and titanium. • Improvement in hardness, elastic modulus and various other mechanical parameters due introduction of metallic (Cu and Ti) interfacial layers. • Increase in indentation load leads to degradation in mechanical properties. In the present study, we explored the effect of metallic interlayers (Cu and Ti) and indentation loads (5–20mN) on the mechanical properties of plasma produced diamond-like carbon (DLC) thin films. Also a comparison has been made for mechanical properties of these films with pure DLC and nitrogen incorporated DLC films. Introduction of N in DLC led to a drastic decrease in residual stress (S) from 1.8 to 0.7GPa, but with expenses of hardness (H) and other mechanical properties. In contrast, addition of Cu and Ti interlayers between substrate Si and DLC, results in significant decrease in S with little enhancement of hardness and other mechanical properties. Among various DLC films, maximum hardness 30.8GPa is observed in Ti-DLC film. Besides hardness and elastic modulus, various other mechanical parameters have also been estimated using load versus displacement curves.