Deformation mechanisms and mechanical properties of single crystal Si under nanotribological loading

The goal of this project is to study the deformation mechanism, mechanical properties of silicon (Si) single crystal under nanotribological loading conditions by using ex situ scanning electron microscopy (SEM) and in situ transmission electron microscopy (TEM). The quantitative correlation between the mechanical properties linked with real time observations of deformation processes will provide a fundamental understanding of the tribological behavior of Si at the nanoscale.

Micro- and Nanoelectromechanical systems (MEMS/NEMS) are an emerging technology widely used in practical applications such as electronics. While these miniaturized devices have been successfully commercialized, the reliability of MEMS/NEMS devices is a concern because of tribological degradation through friction, adhesion and wear induced by the relative motion between components during operation. The wear mechanisms in MEMS/NEMS are fundamentally different from that in macro-scale devices due to scaling effects and the tribological behavior is not well understood, especially at the nanoscale.

In this project, we investigate the size-dependent deformation mechanisms and mechanical properties of Si single crystals under nanotribological loading. With reducing the dimension of the material, the deformation mechanism and mechanical properties are subject to a significant change due to the increase of surface area to volume ratio. In order to investigate the size-dependent tribological behavior of Si, micro- and nanoscratch experiments will be performed on polished single crystal surfaces. The deformation mechanisms will be revealed by extracting samples from the wear tracks using advanced TEM techniques. In addition, to understand the origin of failure by wear, real-time observations of the defect evolution and the correlated load-displacement curves will be obtained by in situ nano-tribological testing in the TEM to identify the nanoscopic wear mechanisms.