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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 94: TEM-based Nanoanalysis and Microstructure of thin films (joint session KFM/CPP)
CPP 94.3: Vortrag
Donnerstag, 19. März 2020, 14:50–15:10, HSZ 301
The role of spatial coherence for the creation of and imaging with atom size electron vortex beams — •Darius Pohl1,2, Stefan Löffler4, Sebastian Schneider2,3, Peter Tiemeijer5, Sorin Lazar5, Kornelius Nielsch2, and Bernd Rellinghaus1,2 — 1Dresden Center for Nanoanalysis, TU Dresden, D-01062 Dresden, Germany. — 2IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany. — 3Institute for Solid State Physics, TU Dresden, D-01062 Dresden, Germany. — 4University Service Centre for Transmission Electron Microscopy, TU Wien, 1040 Wien, Austria. — 5Thermo Fisher Scientific, PO Box 8066, 5600 KA Eindhoven, The Netherlands.
Recently discovered electron vortex beams (EVBs), which carry quantized orbital angular momenta (OAM), are envisioned to be used in combination with measurements of the electron magnetic circular dichroism (EMCD) to determine the magnetic properties of a material in transmission electron microscopes. Since EVBs can be easily focused down to sub-nanometer diameters, this novel technique bears enormous potential for the quantification of spin and orbital magnetic moments with unrivalled lateral resolution. We use specially designed condenser apertures to generate isolated atom size EVBs with user-selectable OAM. Since the "purity" of the beam regarding the chosen OAM depends on the coherence of the electron source, we have used the monochromator in a double aberration corrected FEI Titan3 80-300 microscope to control the degree of this coherence. It will be presented, how a likewise improved coherence will affect the quality of the EMCD measurements.