Three-Dimensional Visualization of Surface Defects in Core−Shell Nanowires

Abstract

The high surface to volume ratio of nanowires makes them attractive for exploiting exotic materials properties and nanoengineering new device structures. To realize these goals, a fundamental understanding of the morphology and growth of the nanowires must be attained in three dimensions, because a two-dimensional projection image of these complex three-dimensional nanomaterials is not sufficient to describe their properties. Scanning transmission electron tomography is used here to obtain three-dimensional tomograms of GaN/AlN core−shell nanowires. This technique reveals the overall morphology and triangular shape of the nanowires, as well as their relation to the catalyst particle, with a resolution of ∼1 nm in all three spatial dimensions. Defects that appear to be in the core of the nanowires in two-dimensional images are shown to be surface defects induced during growth, demonstrating the importance of this three-dimensional technique in analyzing nanomaterials.