Optical depth sectioning of metallic nanoparticles in the aberration-corrected scanning transmission electron microscope

Abstract

Aberration correctors have proved themselves an important addition to the electron microscope. The resulting increased numerical aperture of the objective lens has allowed sub-angstrom resolution [1]. The increased numerical aperture also reduces the depth of field [2], which is just a few nanometres for an aberration-corrected scanning transmission electron microscope (STEM). We can use this reduction to provide threedimensional information by optically sectioning our sample much like in confocal optical microscopy, or probe specific depths in our sample. While we do not expect this technique will be able to compete with tomography for spatial resolution, the advantage is that data acquisition is a matter of minutes as opposed to hours and specific depths within a sample can be probed without the need for a lengthy reconstruction.