Seeing atoms at sub-Angstrom resolution with aberration-corrected TEM

Hardware and software correction of spherical aberration have each produced sub-Angstrom images, and allowed the imaging of light atoms such as oxygen. The LBNL One-Angstrom Microscope (O Angstrom M) combines a modified CM300FEG/UT TEM with FEI focal-series reconstruction software to achieve sub-Angstrom resolution to 0.78 Angstrom. Modifications include hardware correction of 3-fold astigmatism to 0.68 Angstrom and information limit extension to 0.78 Angstrom. The O Angstrom M can image atoms as light (small) as nitrogen, carbon, and lithium. Focal-series reconstruction (FSR) compensates for imperfect objective lens transfer, and provides improvement over any single image. Reconstructed O Angstrom M images, assembled from 20-member focal series, are "cleaner" than single-shot images, due to lack of second-order contributions. However, second-order components can be removed from single images by subtracting a minimum-contrast image, thus extending the interpretable specimen thickness. In general, TEM images are able to depict atom positions just as well as do FSR images, provided both have the same resolution