Nanoindentation study of deformation-resistant Al/a-Si core–shell nanostructures

A nanoindentation study was performed on a novel type of core–shell nanostructure (CSN) that consists of a nanostructured core layer covered by a nanoscale shell layer. The CSNs were formed by first depositing an Al film with protruding nanostructures onto a smooth Si surface through thermal evaporation and then depositing an amorphous Si film by plasma-enhanced chemical vapor deposition on top of the Al layer. It was found that these CSNs have very high yield strength of about 19 GPa. They can also sustain about 23% engineering strain without fracture. Furthermore, these CSNs show complete recovery of plastic deformation upon repetitive nanoindentation. Such a novel type of CSN should find applications in many areas, including nanodot-based magnetic recording, nanoimprinting lithography, microelectromechanical systems, surface wetting and biomedicine, where mechanical integrity of the nanostructures is of paramount importance.