Measuring elastoplastic properties of thin films on an elastic substrate using sharp indentation

Nanoindentation is a technique commonly used for measuring material elastoplastic properties. In this study, we extend the indentation analysis to an elastoplastic thin film on an elastic substrate. With the assistance of the substrate effect, the film elastic modulus, yield stress and work hardening exponent can be measured from one simple sharp indentation test with moderate penetration depth. The film elastoplastic properties and film/substrate mismatches are varied over a large range in the forward analysis, and an effective reverse analysis algorithm is established to deduce film properties from the indentation load–displacement curve. Comprehensive analyses are carried out to examine the accuracy, error sensitivity, and effectiveness of the proposed method. Both nanoindentation and bulge tests are carried out on a Cu film/Si substrate system, and the good agreement shows that the new film indentation technique may be applied in practice.