Influence of the residual stress on the nanoindentation-evaluated hardness for zirconiumnitride films

The influence of the residual stress on the evaluated hardness and modulus for zirconium nitride films has been investigated using nanoindentation experiments in this work, and a variety of indentation load–displacement curves have been examined by analyzing the contribution of the residual stress to the indentation load. Atomic force microscopy (AFM) is performed to reveal the behavior of deformation (e.g. pile-up) around the indent on the surface of the film. The pile-up occurs for the film under a compressive stress, and is enlarged with increasing the compressive stress, which leads to that the actual contact area by indenter significantly deviates to the one calculated by Oliver–Pharr method. After correcting the contact area contributed by pile-up via AFM experiments, the residual stress does not affect the nanoindentation-measured hardness and modulus.

► The pile-up occurs for the zirconium nitride film under a compressive stress.
► The pile-up is enlarged with increasing the compressive stress.
► The Oliver–Pharr method exaggerates the influence of the stress on hardness.