Determination of the elastic behavior of silicon nanowires within a scanning electron microscope

Abstract

Three-point bending tests were performed on double-anchored, < 110 > silicon nanowire samples in the vacuum chamber of a scanning electron microscope ( SEM) via a micromanipulator equipped with a piezoresistive force sensor. Nanowires with widths of 35nm and 74 nm and a height of 168nm were fabricated. The nanowires were obtained monolithically along with their 10 mu m tall supports through a top-down fabrication approach involving a series of etching processes. The exact dimension of wire cross sections was determined by transmission electron microscopy ( TEM). Conducting the experiments in an SEM chamber further raised the opportunity of the direct observation of any deviation from ideal loading conditions such as twisting, which could then be taken into consideration in simulations. Measured force-displacement behavior was observed to exhibit close resemblance to simulation results obtained by finite element modeling, when the bulk value of 169gpa was taken as the modulus of elasticity for < 110 > silicon. Hence, test results neither show any size effect nor show evidence of residual stresses for the considered nanoscale objects. The increased effect of the native oxide with reduced nanowire dimensions was captured as well. The results demonstrate the potential of the developed nanowire fabrication approach for the incorporation in functional micromechanical devices.