Parallel-beam diffraction and direct imaging in an aberration-corrected STEM

Abstract

Aberration-corrected scanning transmission electron microscopes (STEMs) are versatile instruments that can perform many types of investigations. The main use of such microscopes has so far been in direct imaging and analysis, but they are equally well suited to performing diffraction studies and combined diffraction+imaging experiments. The various optical modes needed for such operating modes are reviewed. They include producing electron beams with angular spreads as narrow as a few μrad, and conical precession scans with scan angles >50 mrad. © 2012 Springer Science+Business Media Dordrecht.