Photoelectron Spectroscopy and Microscopy in 4D

Cross section of the spectrometer [Schönhense et al., J. Electron Spectrosc., 200 (2015), pp. 95–119]

Cross section of the spectrometer [Schönhense et al., J. Electron Spectrosc., 200 (2015), pp. 95–119]

Earliest Start: May 2018

Topic

Electrons photo-emitted from a sample can either be used to get a microscopic image of the sample or to map the electronic bandstructure. In our momentum microscope, we can do both. By changing the voltages of the electron lenses, we easily switch from real space to momentum space and back. Analyzing the energy and angular momentum of the sample then allows to map the complete bandstructure in 3 dimensions.

In the real space imaging, we use the instrument as a photoemission electron microscope (PEEM). When doing the bandstructure mapping, the drift tube of the microscope operates as a time-of-flight spectrometer (ToF). Additionally, the momentum microscope is equipped with a second flight tube for spin-resolution, which gives us a fourth dimesion to measure in.

During your master thesis, we will do the first measurements in the ToF operation mode of this instrument and start to set up a spin filter. The PEEM mode is already established and was used to image the photo-switching of molecular monolayers of azobenzene on gold. To start the ToF operation, a small laser setup has to be adjusted first to provide light pulses for the flight-time measurement. The investigations on switching molecules are planned to be continued during your thesis followed by first measurements on molecular spin-interfaces.

To Do List

  • Adjust the pulsed laser setup comprising a Ti:Sapphire oscillator and a second harmonic generation
  • First measurements on metallic samples (Cu, Au) for calibration
  • Prepare molecular monolayers
  • Measurements of the molecular switching behavior
  • (Set up a new spin filter)

You Will Learn:

  • Almost everything about photoemission
  • Working with short-pulsed lasers and ultrahigh vaccum
  • A lot about molecular dynamics
  • Some Labview programming to improve and extend the measurement software

If Interested, Write To:

Beatrice Andres <andres[at]physik.fu-berlin.de>