Abstract

The ability to correct the spherical aberration inherent in the electron lenses of the scanning transmission electron microscope is creating a number of new opportunities. In this talk we shall explore a number of ways that we can use aberration-corrected STEM for three-dimensional investigations of materials.

The first application makes use of the fact that correction of spherical aberration leads to enhanced visibility of supported nanostructures, and has allowed the crystal structure of inorganic MoSI nanowires to be determined by recording high resolution images from a variety of orientations.

A second approach is to make use of the reduced depth of field that results from aberration correction. Bloch wave calculations for zone-axis crystals demonstrate that there are two scattering effects that can displace the crossover from the desired focal plane within the sample, and that certain depths may be completely inaccessible.

Finally, we will discuss the possibility of performing optical sectioning using a double aberration-corrected instrument operating in a confocal mode. Recent calculations analysing this new imaging mode will be presented, and some experimental data demonstrating the feasibility of the confocal trajectories.