Scanning transmission electron microscopy: Albert Crewe's vision and beyond

Some four decades were needed to catch up with the vision that Albert Crewe and his group had for the scanning transmission electron microscope (STEM) in the nineteen sixties and seventies: attaining 0.5 Å resolution, and identifying single atoms spectroscopically. With these goals now attained, STEM developments are turning toward new directions, such as rapid atomic resolution imaging and exploring atomic bonding and electronic properties of samples at atomic resolution. The accomplishments and the future challenges are reviewed and illustrated with practical examples.

► TV-rate STEM imaging of heavy atoms is demonstrated.
► DNA sequencing by STEM dark field imaging should be possible at a rate of 106 bases/s.
► Individual silicon atom impurities in graphene are imaged atom-by-atom.
► Single atoms of nitrogen and boron incorporated in graphene are imaged spectroscopically.
► Bonding of individual atoms can be probed by analyzing the fine structures of their EEL spectra.