Nanoscale Measurements of the Real Area of Contact and Comparison to Theoretical Models

In this study, a new experimental method is proposed to measure the real area of contact between a alumina sphere and an Al surface based on the adhesive transfer of the Au film and the Scanning Electron Microscope (SEM) in the back-scattered mode. A thin film of Au is sputtered on the alumina sphere before the indentation with the Al surface. After indentation, the interfaces of the alumina sphere and Al surface are observed by SEM. The contact area can be identified based on both the distributions of the alumina and Au on the alumina sphere and Al surface, respectively. The measured contact area at different nominal pressures are compared to predictions made by several popular theoretical elastic-plastic rough surface contact models.