Dresden 2020 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: TEM-based Nanoanalysis and Microstructure of thin films (joint session KFM/CPP)

KFM 14.3: Talk

Thursday, March 19, 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 Pohl^1,2, Stefan Löffler⁴, Sebastian Schneider^2,3, Peter Tiemeijer⁵, Sorin Lazar⁵, Kornelius Nielsch², and Bernd Rellinghaus^1,2 — 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.