Photoemission electron microscope (PEEM)
Figure 7: Photo of the PEEM (click for an enlarged picture).
| Spatial resolution: |
down to ~50 nm depending on sample |
| Electron energy resolution: |
0.2 eV |
| Sample temperature: |
120 K < T < 1'800 K |
| Field of view: |
1 - 50 mm diameter |
The permanent endstation of the SIM beamline is a Photoemission Electron microscope (PEEM) (Model: LEEM III,
Elmitec GmbH).
It allows to image samples using the photoelectric effect with very high spatial resolution. With an additional energy analyzer (to be installed in March 2002) these 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). A more comfortable prepchamber is being designed.
When retracting the sample, the light passes through the PEEM and can be used in a second endstation
supplied by the user. Here an unfocussed beam of about 1 x 3 mm2 is available.
For more information on PEEM for example lookup the web page of the LEEM User Community.
Sample conditions
The PEEM is a surface sensitive instrument. Its depth of view is limited by the inelastic mean
free path of the photoelectrons which is typically ~5nm. The PEEM operates in UHV and
with high acceleration voltage (Va = 20kV) to accelerate the
inelastically scattered photoelectrons into the microscope where they are imaged producing a magnified image.
For successful imaging in the PEEM the sample should meet the following conditions:
- sample dimensions: diameter < 10mm, thickness ~0.1 - 3mm
- UHV compatible (p < 10-7mbar)
- flat and conducting surfaces are likely to produce high quality images with good spatial resolution.
For more information please contact the beamline scientist (Frithjof Nolting or Arantxa Fraile Rodriguez).
