Transverse shear stress within surface layer and its effects

When the transverse shear stress within a surface layer is taken into account, what happens in the deformation of micro- or nanoscale solids? The relevant problems are investigated by analyzing the deformation of a micro- or nanosized solid ellipsoid. The results show that both the stress and the deformation of a micro- or nanosized ellipsoid increase after the transverse shear stress within the surface layer is introduced, and that the maximal stress always occurs at both ends of the long axis of the ellipsoid. Unlike the prediction given by the Gurtin–Murdoch model, the calculation coming from the model of this paper predicts that the micro- or nanosized ellipsoid subjected to hydrostatic pressure contracts radially in the middle section and expands radially on both sides of the middle section. This difference provides an experimental standard to verify two models.

Surface effects at the nanoscale based on Gurtin’s theory: a review

The fields of nanotechnology and nanoscience are full of opportunities and challenges. The needed modification of classical continuum mechanics to account for the dramatically novel characteristics and phenomena determining the mechanical response of nanomaterials/structures remains an ambitious goal pursued by mechanics researchers. The theory of surface elasticity proposed by Gurtin and Murdoch has been shown to be an important tool in theoretical nanomechanics. In this paper, we present an overview of recent advances in application of surface elasticity theory at the nanoscale. In particular, we focus on the elastic and plastic deformation, vibration and buckling, fracture and contact behavior of nanoscale solids from one dimension to three dimensions. We hope that this contribution can provide a valuable insight into nanomechanics analysis methods by taking surface effects into account. The results may help to bridge the gap between conventional mechanics and findings from simulation and experiment, in such areas as multifunctional material and micro-electro-mechanical systems.

Quantitative analysis of silicon oxide using EELS

Silicon oxide exists as a continuous solid solution of Si and O (i.e., Si to SiO2), and its band gap energy (Eg) depends on the oxygen content in the system. Si is a semiconductor (Eg=1.1eV) but SiO2 is an insulator (Eg=9eV). Substoichiometric oxide SiOx, where 0<x<2, is a semi-insulator. With its extensive applications in electronic and photonic devices, quantitative analysis for the structure and composition of silicon oxide synthesized by various methods becomes increasingly important to understand its structure/properties relationships. EELS, when coupled to a TEM with a field emission source, is a powerful analytical technique for obtaining a host of spatially resolved information from nanoscale solids. In this paper, several examples of applications of high spatial resolution EELS for quantitative analysis of silicon oxides will be illustrated, with brief descriptions of experimental and data quantification procedure.