Electronic Structure - G. H. Fecher
Theory and Experiment
Hard X-ray photoelectron spectroscopy (HAXPES) is a well-adaptable non-destructive technique for the analysis of electronic bulk states, buried films and interfaces. This technique provides important information for the design of new Heusler compounds.
HAXPES is a photoemission technique that employs hard X-ray (photon energy > 3000 eV). The excitation by hard X-ray results in the emission of electrons with high kinetic energies and, consequently, in very large probing depth. The probe of real bulk states allows a more reliable comparison between experimental spectra and theoretical predictions in Heusler compounds.
- Chemical Analysis
- Electronic Structure
- Depth Profile
- Crystal Ordering
- Magnetic Ordering
HAXPES is a versatile technique
HAXPES is able to determine the symmetry of the states composing the valence band. Circularly polarized hard X-rays allows the investigation of magnetic properties in multilayer structures. Even structural properties can be investigated by using the angular distribution of the high kinetic energy photoelectrons.
Our group has extensively investigated the electronic properties of Heusler compounds for spintronics, magneto shape memories and thermoelectric applications. We have studied the changes in the electronic structure upon chemical substitution or induced phase transitions. Many properties of Heusler compounds are essentially connected to the valence band, which is formed by bonding and hybridized states. The measurement of valence band states by HAXPES is used as validation and feedback for the calculation and tailoring of the Heusler properties. Using HAXPES, we are able to investigate the interfaces of multilayer structures, which is important for devices applications (e.g. magneto tunneling junctions). More recently we have investigated also new materials as topological insulator and new phases induced by ionic liquid electrolyte.