We have demonstrated the utility of nanoindentation as a rapid characterization tool for mapping shape memory alloy compositions in combinatorial thin-film libraries. Nanoindentation was performed on Ni–Mn–Al ternary composition spreads. The indentation hardness and the reduced elastic modulus were mapped across a large fraction of the ternary phase diagram. The large shape memory alloy composition region, located around the Heusler composition (Ni2MnAl), was found to display significant departure in these mechanical properties from the rest of the composition spread. In particular, the modulus and the hardness values are lower for the martensite region than those of the rest of the phase diagram.

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The reliability of nanoindentation results can depend critically on an accurate assessment of the machine compliance term. The common practice is to determine the machine compliance from a small reference specimen, then apply its value to a much larger wafer-supported library. The present study investigates the validity of this approach by thoroughly testing bare 76.2 mm diameter, 410μm thick Si(100) wafers mounted on two vacuum chucks of different design. We find that the small-sample value of the machine compliance is adequate for the majority of the wafer, including areas directly over vacuum rings and a circular center port of ordinary dimensions. However, vacuum chucks with a tweezer slot should be avoided in combinatorial materials science applications. But even in the absence of a tweezer slot, it may be necessary to generate an accurate machine compliance map for the wafer perimeter if the thin-film library extends beyond the outermost vacuum ring to the wafer edge. The Young’s modulus and the hardness of silicon are found to be 169±3GPa and 12.2±0.2GPa, respectively, over well-mounted regions of the wafer; both values are in good agreement with the literature.

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