Přednáška Dr. Ondřeje L. Křivánka
Dne 14. března 2017 v 15:00 v přednáškovém sále Fyzikálního ústavu AV ČR Na Slovance.
Electron-optical methods for molecular and atomic-level characterization
Monochromated, aberration-corrected scanning transmission electron microscopes (MAC-STEMs) are able to form intense electron probes as small as 0.5-1 Å in diameter, analyze single atoms spectroscopically (by electron energy loss spectroscopy (EELS) or energy-dispersive X-ray spectroscopy (EDXS)), detect vibrational EEL spectra, and perform many other types of experiments that we did not think would become possible as recently as 5 years ago.
Nion has pioneered many of these advances, by developing the first practical STEM aberration corrector, and subsequently a whole new electron microscope (the Nion UltraSTEM) that includes innovations such as very flexible electron optics, a corrector for all aberrations up to fifth order, an extremely precise and stable sample stage, and an ultra-high vacuum (UHV) sample chamber. The STEM is routinely able to image and individually probe single atoms while they remain in-situ, and to acquire large-area chemical maps at atomic resolution. In 2013 we introduced a new type of a monochromator, which allows materials to be probed by vibrational EELS carried out with better than 10 meV energy resolution and about 1 nm spatial resolution, as well as damage-free vibrational analysis in an “aloof” mode.