Prospects for 3D, nanometer-resolution imaging by confocal STEM

Confocal STEM is a new electron microscopy imaging mode. In a microscope with spherical aberration-corrected electron optics, it can produce three-dimensional (3D) images by optical sectioning. We have adapted the linear imaging theory of light confocal microscopy to confocal STEM and use it to suggest optimum imaging conditions for a confocal STEM limited by fifth-order spherical aberration. We predict that current or near-future microscopes will be able to produce 3D images with 1 nm vertical resolution and sub-Ångstrom lateral resolution. Multislice simulations show that we will need to be cautious in interpreting these images, however, as they can be complicated by dynamical electron scattering.