Nanomechanical characterization of thermally evaporated Cr thin films - FE analysis of the substrate effect

We study the substrate effect on the deformation and hardness behaviour of chromium thin films using nanoindentation technique. Two different substrates namely Si (100) and AISI-304 SS are used in order to obtain a soft film on a hard substrate and a hard film on a soft substrate combination. Typical hardness variations for the two combinations are obtained. It is also observed that Cr thin films deposited on two different substrates deform distinctly. Radial cracks are found to develop in the case of Cr film on Si whereas circumferential cracks are produced in the case of Cr film on SS substrate. Using 2-D finite element analysis, it is found that the substrate not only affects the development of plastic zone but also the stress distribution in the films which results in observed distinct hardness and deformation behaviour.