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Photoelectron emission microscope (PEEM)

Photoelectron emission microscope for spectroscopic imaging and spot analysis

Figure 1
Photograph of the PEEM chamber and its major components

This UHV-system houses a photoelectron emission microscope (PEEM) and a 4-grid low-energy electron diffraction (LEED) system, which can also be used for Auger electron spectroscopy (AES). In addition, the chamber is equipped with tools for sample preparation (ion sputter gun, sample heating, electron beam evaporator for metals and sources for deposition of organic molecules) and a load-lock system for easy sample insertion. To increase the mechanical stability, the whole vacuum system rests on three air damping legs.

The PEEM is equipped with an integrated sample stage for ultimate stability and an imaging high-pass energy filter for spectromicroscopy.[1]
  A high-pressure mercury (Hg) UV-lamp with an emission maximum at 4.9 eV acts as a standard photon source. Additional light sources include a Xenon lamp (7.8 eV) and a He-I,II VUV source (21.2 eV, 40.8 eV). The light of the Hg lamp can be also polarized. The systematic variation of the polarization give right for an additional contrast. [2]

The reflected light is detected by two spectrometer, one of each linearly, orthogonal polarized component of the light. This particualr setup allow therefore the simultanous and synchronized acquisition of PEEM movies and polarization dependent differential reflectance spectra during the deposition of organic thin films. [3]
 
The system allows the in-situ and real-time observation of the growth of organic molecules.

The already quite versatile set-up is supplemented by a UHV scanning probe microscopy system (combined atomic force (AFM) and scanning tunnelling microscopy (STM) system). An additional upgrade made it possible to cool the sample down to 50 K during STM/AFM investigation.

The combined STM/AFM - PEEM setup allows studying structures all the way from the atomic scale up to 150 µm.

References
[1] T. Wagner, D. R. Fritz, and P. Zeppenfeld. Standing and at lying \alpha-6T molecules probed by imaging photoelectron spectroscopy. In: Organic
Electronics 12 (2011), pp. 442446. doi: 10.1016/j.orgel.2010.12.011.

[2] T. Wagner et al. The growth of \alpha-sexithiophene films on Ag(111) studied
by means of PEEM with linearly polarized light. In: Ultramicroscopy 159
(2015), pp. 464469. doi: 10.1016/j.ultramic.2015.06.013.

[3] A. Navarro-Quezada et al., Polarization-dependent differential reflectance
spectroscopy for real-time monitoring of organic thin during growth. In: The
Review of Scientific Instruments 86 (2015), p. 113108. doi: 10.1063/1.
4936352.

For more information please contact: Thorsten Wagner or Peter Zeppenfeld