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Surfaces / Interfaces: Microscopy (SIM) Beamline
The SIM beamline produces a high flux of soft X-rays with variable polarization from an undulator source. The beamline has a Photo-Emission Electron Microscope (PEEM) (Model: LEEM III, Elmitec GmbH) as a permanent endstation open to user via the SLS proposals system. The instrument allows to image samples using the photoelectric effect with very high spatial resolution (100 nm), chemical and magnetic sensitivity. With an energy analyzer the excited photoelectrons can be energy-selected. In addition to illumination by X-rays, illumination by low energy electrons is possible. In this low energy electron microscopy (LEEM) mode additional contrast mechanisms are available.
The PEEM is equipped with a small preparation chamber (sputtering, heating, load-lock). In addition, a more complete preparation system is available with a load-lock, LEED and Auger, several evaporation sources, rotatable electromagnetic coil, ion etching and electron bombardment heating.
Users can apply for beamtime with the PEEM or with their own endstation (after prior consulation with the beamline scientist).
The SIM beamline is operated by the Microscopy and Magnetism Group.
| Energy range | 90-2000 eV |
|---|---|
| Flux (1 keV) | 1 x 1015 photons/s/0.1%BW/ 0.4 A |
| Focused spot size | 30 µm x 100 µm (V x H) |
| Spectral resolution | > 5000 |
| Polarization | Linear: 0o (horizontal) to 90o (vertical) Circular: right / left |
| Endstation ES1 | Photo-emission electron microscope with spatial resolution = 70 nm, variable sample temperature: 100 - 1'800 K. |
| Endstation ES3 | XMCD chamber for total electron yield (TEY) measurements in applied field (130 mT) and variable sample temperature (5 - 450 K). |
| Endstation ES4 | Resonant x-ray scattering (RESOXS) and near ambient pressure photo-emission (NAPP). These endstations belong to user groups and can only be used in collaboration with them. |
Current Highlights and News
Single femtosecond laser pulse excitation of individual cobalt nanoparticles
The interaction of light and magnetism at the nanoscale is a topic of fundamental interest and with potential impact to future spintronics applications. in this work we address theoretically and experimentally the effect of femtosecond laser pulse excitation on the magnetic, structural, and chemical stability of individual magnetic cobalt nanoparticles including the role of the substrate or matrix. Eventually, we discuss possible pathways to achieve laser-induced magnetic switching in individual nanostructures.
This work has been highlighted as "Editors' Suggestion" in Physical Review B.
Remote Operation of the PEEM Endstation
We have recently upgraded the PEEM endstation at the SIM beamline to enable remotely controlled experiments via internet and mailed-in samples. Sample positioning and tilt control is now possible by means of a motorized sample stage. A newly developed computer controlled switchbox is available for remote temperature control and in situ application of electric or magnetic fields to the sample.
Novel optics enable better X-ray Free Electron Laser experiments
Our research on multifocus off-axis zone plates was accepted in “Optica”, the highest impact journal of the Optical Society of America. In the paper we report on different ways to combine focusing and beam-splitting functionalities in one single optical element.