A new method for mechanical testing of thin films: Application to aluminum

A new method for measuring plastic properties of thin films deposited on a substrate is presented. Micrometric cylindrical specimens with the axis perpendicular to the film surface were prepared by milling out the surrounding material using the focused ion beam technique. Such specimens were deformed by means of a nanoindenter outfitted with a flat diamond tip. An equivalent to the macroscopic compressive curve was obtained. Elastic modulus and hardness of the film were then measured using a Berkovich tip. The precise knowledge of the gage length and the independent measurement of elastic properties enable the accurate determination of the stress–strain curve. As compared with the results published in the literature on the specimens with the same dimensions, the studied material deforms less heterogeneously, probably as a consequence of the symmetric crystallographic orientation of the specimens.