Deformation and fatigue resistance of Al/a-Si core-shell nanostructures subjected to cyclic nanoindentation

Abstract Nanostructure-textured surfaces can reduce friction and adhesion of micro- and nano-electromechanical systems (MEMS/NEMS). For MEMS/NEMS incorporating moving parts, the fatigue properties of nanostructures pose a challenge to their reliability in long-term applications. In this study, the fatigue behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), bare hemispherical Al nanodots, and a flat Al/a-Si layered thin film have been studied using nanoindentation and nano-scale dynamic mechanical analysis (DMA) techniques. Fatigue testing with nano-scale DMA shows that the deformation resistance of CSNs persists through 5.0 × 10 4 loading cycles at estimated contact pressures greater than 20 GPa. For bare Al nanodots which lack the hard a-Si shell, significant nanostructure deformation results due to repeated cyclic loading. In addition, for the Al/a-Si layered thin film which lacks the geometric and dislocation confinement properties of CSNs, cyclic loading results in fatigue failure of the a-Si layer. Even at elevated contact pressures, CSNs demonstrate none of the failure mechanisms exhibited by the other two control structures. The unique properties displayed by CSNs when subjected to fatigue testing establish their prolonged reliability and durability when implemented in micro- and nano-scale applications.