Energetic Analysis of Al/TiN Multilayered Films by Nano-indentation

In order to discuss mechanisms of hardness enhancement of Al/TiN multilayered thin films, elastic and plastic deformation behaviors of the multilayered films have been investigated by using dissipated and elastic energies evaluated from a load-displacement curve of nanoindentation. The Al/TiN multilayered films were deposited by dc magnetron sputtering. Thickness of Al layers was varied from 3 to 100 nm, and that of TiN layers was varied from 16 to 500 nm in correspondence with the variation in the number of layers from 60 to 2. A hardness enhancement by up to 10% compared to a monolithic TiN film was observed for a 20-layerd film with an Al layer thickness of 10 nm and a TiN layer thickness of 50 nm. A minimum dissipated energy was observed for a film with Al layer thickness of 5 or 10 nm. In contrary, elastic energy showed a maximum for the film. The reduction in the dissipated energy for a film with a thin Al layer implies that the pinning effect for propagation of dislocations at an interface between Al and TiN layers suppresses plastic deformation, resulting in the enhancement in microhardness.