Lawrence Berkeley National Laboratory

Twenty-five years ago, the Cowley group at ASU pioneered the use of transmission electron microscopy for high resolution, and achieved unique images showing the content of the crystal unit cell at better than 4 Angstrom resolution. Subsequent improvements in resolution enabled researchers to pinpoint heavy atom positions at 2 Angstrom resolution, followed by light atoms (down to lithium) at 1 Angstrom resolution. These progressive improvements in resolution (as well as parallel improvements in holography, EELS and EDS) have earned HRTEM a well-deserved position as an essential tool for the characterization of materials. HRTEM at sub-Angstrom resolution will play an essential role in the verification of structures researched in the emergent nanotech revolution. Sub-Angstrom resolution has been demonstrated by the Berkeley O Angstrom M (Angstrom Microscope) project using focal-series reconstruction of the specimen exit surface wave. Results from the O Angstrom M foreshadow those to be expected from next-generation TEMs with Cs-corrected lenses and monochromated electron beams.