New Insight into Pile-up in Thin Film Indentation

A new method of accurately and reliably extract the actual Young’s modulus of a thin film on a substrate has been developed. The method is referred to as the discontinuous elastic interface transfer model. The method has been shown to work exceptionally well with films and substrates encompassing a wide range of elastic moduli and Poisson ratios. The advantage of the method is that it does not require a continuous stiffness method and can use the standard Oliver and Pharr analysis and the use of a predictive formula for determining the modulus of the film as long as the film thickness, substrate modulus and bulk Poisson ratio of the film are known. However, when there is much pile-up during the indentation process in a softer film, the experimental data does not follow the predictive formula but instead follows a similar model with a single Poisson ratio between the film and the substrate.