Low-Current Focused Ion Beam Milling for Freestanding Nanomaterial Characterization

Abstract

Techniques for the fabrication of one-dimensional or quasi-one-dimensional nanowires as well as to enable studies of the compositional, structural, and electrical properties of freestanding individual nanoobjects are of great importance, for instance, to observe quantum size effects and build quantum information devices. In this chapter, a technique of low-current focused ion beam (FIB) milling for two kinds of applications, namely, the selective felling of freestanding nanoobjects in a well-controllable way and the size reduction of both lateral and freestanding tungsten composite nanostructures, is presented. To fell a freestanding nanoobject, parameters such as the angle of the incident ion beam with respect to the nanoobject long axis, the cutting point, and the ion beam current were carefully chosen for controllable felling. To thin a nanoobject, different exposure times and ion beam currents were used to control the final size, thinning rate, and accuracy of a group of nanowires, or an individual nanowire, or even a portion of a nanowire by site-specific milling. After felling or thinning with low-current ion beam, no obvious structural and electrical property changes were observed for nanoobject grown with FIB-induced deposition. These results suggest that FIB milling is applicable in felling freestanding nanoobjects for the investigation of the properties of selected individuals, and it is also a potential approach for controllable size reduction enabling the observation of size and quantum effects.