Methods

Electron Microscopy group

Covering a broad range of magnifications ranging from optical microscopy over scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) down to sub angstrom resolution imaging using state of the art Cs corrected transmission electron microscopy (TEM), we study the structural characteristics of catalysts. Structural information is complemented with information about the elemental composition which is acquired using appropriate techniques for different size dimensions of the analyzed volume. The techniques range from X-ray fluorescence spectroscopy for average composition to energy dispersive X-ray (EDX) spectroscopy and EDX mapping in the electron microscope for more localized information. Furthermore, electron energy loss spectrometry (EELS) is used to provide further details about the elemental composition and electronic structure. Interpretation of the experimental data is supported by image simulations on the structure side and band structure calculation of the electronic structure and the simulation of EELS spectra on the other.

TEM

  • high resolution imaging
  • bright field/dark field imaging
  • selected area diffraction

 

STEM

  • fast spot scanning
  • elemental mapping

EDX

  • Qualitative and quantitative elemental analysis

EELS

  • qualitative elemental analysis
  • electronic structure

Theory

  • density functional theory based calculations of the electronic structure
  • simulation of the finestructure in EELS spectra

Image simulation

  • particle shape
  • focal series reconstruction
  • high-resolution image simulation

SEM

Secondary Electron (SE) detector

  • low voltage imaging
  • surface morphology

  • Diffractogramm Tableau
    • diffraction parameter
    • diffraction tableau
    • aberration
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