Endstations

The permanent endstation of the SIM beamline is a Photoemission Electron microscope (PEEM) (Model: SPELEEM, Elmitec GmbH) with a motorized and rotatable sample stage. It allows one to image samples using the photoelectric effect with very high spatial resolution. With an additional energy analyzer these photoelectrons are then energy-selected. In addition to the grazing incidence X-ray illumination (16°), the sample can be illuminated by low energy electrons. 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), while a larger preparation system equipped with LEED and e-beam evaporators, is also available. 

When the sample is retracted, the light passes through the PEEM and can be used in a second endstation further downstream either focussed or unfocussed.

PEEM is a surface sensitive technique. Its depth of view is limited by the inelastic mean free path of the photoelectrons which is typically ~5 nm. The PEEM operates in UHV and with a high voltage (V_a = 10-20 kV) to accelerate the excited photoelectrons into the microscope lenses to produce a magnified image of the intensity of the locally emitted electrons. 

For successful imaging in the PEEM the sample should meet the following conditions:

• sample dimensions: diameter < 10 mm, thickness ~0.1-3 mm
• UHV compatible (p < 10^-8 mbar)
• flat and conducting surfaces are likely to produce high quality images with good spatial resolution.

For more information please contact the beamline scientist (Carlos Vaz or Armin Kleibert).

A soft x-ray ptychography microscope (SOPHIE) operated by the Microspectroscopy Group enabling high spatial resolution (~5 nm) soft x-ray spectromicroscopy.