Ultrahigh-resolution Scanning Transmission Microscopy with Sub-?ngstrom-Sized Electron Beams...

The scanning transmission electron microscope(STEM)with an annular dark-field(ADF)
detector provides atomic-resolution incoherent images, whose resolution is dominated, to a
good approximation, by the size of convergent electron beams. Improving a spherical aberra-
tion of microscope objective lenses has been successful in converging the beam into sub-� scale,
promising a remarkably higher resolution for STEM. Here we describe the performance of
aberration-corrected 300kV-STEM - the world-best STEM available today. The results clearly
demonstrate that a sub-�ngstrom resolution has been indeed achieved for not only simple
structures but also structurally complex systems(quasicrystals).