Contact stress analysis of lightly compressed thin films: Modeling and experimentation

Abstract

Although a number of models have been developed to describe the contact between nominally smooth surfaces, very few of these models have been validated with experiment. Therefore, in this study, an asperity-scale experimental contact measurement was conducted and compared to the predictions of two contact models. The experimental component of this study involved a flat diamond punch tip on a nanoindenter, which was used to compress a thin film that was lithographically patterned into isolated raised squares. This experimental method was developed in order to measure the predominantly elastic load response of the surface asperities on one of the isolated raised topography islands. The experimental measurements were compared to the predicted load responses of an existing analytical contact model as well as a finite element contact model that incorporated the topography of the raised island into its formulation. The predictions of both the models were shown to have reasonable agreement with the experimental data. The modeling results were also used to provide greater depth of insight into the physics of the flat punch compression.