The purpose of this paper is to find a reliable method for determining the hardnesses of soft metallic thin films on hard substrates. Based on the nanoindention experimental data for a 504 nm Au thin film deposited on glass substrate system, several possible methods are applied and the results come from them are compared. The results reveal that the Oliver-Pharr method is strongly influenced by the material pile-up behavior and substrate effect that leads to an erroneously overestimated hardness. However, the methods based on traditional area calculations by SEM image, work of indentation principles during the indentation cycle and constant modulus assumption calculations all can effectively avoid the effect of pile-up and minimize that of substrate. Among three, the results from indentation method are obviously much higher than those from other two. Hence we argue that the results by SEM image method and constant modulus assumption calculations are more reasonable.

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