- Imaging surface and subsurface structures by photoemission
- Hard X-ray photoelectron spectroscopy (HAXPES) of small structures
Specific information on the method:
- Photoemission by 3-10 keV photons delivered by synchrotron beamline
- Microscopic imaging of (sub-) surface structures by energy-filtered photoelectrons
Specific information on the equipment/instrumentation:
The HAXPEEM instrument is an energy-filtering photoemission microscope for laterally resolved hard x-ray photoemission spectroscopy with resolution in the range of 500nm (spatial) and 400meV (energy). Electrons photoemitted by hard x-rays gain high kinetic energies leading to long inelastic mean free paths inside solids, which in turn enables (non-destructive) spectroscopic access to regions up to several nm beneath the surface.
Samples must be UHV-compatible and stable under illumination by hard x-rays (3-10keV photon energy). Favored sample size is 10mm x 10mm x 1mm. Samples must be conductive and flat. Structures of interest should be between 1µm and 50µm in size. Access to hard x-rays is dependent on regular beamtime proposal at PETRA III synchrotron facility (Hamburg).
Examples of typical analytical questions:
- determination of chemical composition of buried structures / interfaces
- clarification of electronic structure in bulk material
- observation of chemical changes induced by electric current / voltage beneath thin (some nm) metal electrodes
Fields of research:
- Fundamental research on electronic structure of matter
- Resistive switching phenomena in oxide and chalkogenide materials