Electron Microscopy

 

Central Facility for Electron Microscopy (GFE) of RWTH Aachen University

© GFE High resolution Transmission Electron Microscope FEI Tecnai F20 with imaging energy filter (Gatan GIF 2000), EDX (EDAX) and HAADF-detector.  

Nanoanalytics in the electron microscope have always played a central role in the characterization of catalytically active systems. Several complementary methods allow nowadays the fast and efficient analysis of the nanoscale structures and reactive centers of a catalyst, often down to the atomic level.

The most frequently used nanoanalytical instrument for this purpose is the transmission electron microscope (TEM). In this context, another device, the Focused Ion Beam Workstation (FIB) plays another important role in the analytical investigation of supported catalysts. In contrary to the classical methods of preparation, the FIB workstation allows the targeted selection of the sampling site, from which the electron-transparent lamella is extracted for the subsequent TEM analysis. The sample thicknesses of a typical FIB lamella ranges between 30 and 100 nanometers, which is perfect for high-resolution imaging and all spectroscopy based methods.

Two transmission electron microscopes equipped with field emission guns and state of the art analytical attachments (X-ray fluorescence analysis with an EDX spectrometer, energy filter and dark field detector for Z-contrast imaging) are available at our facility. These instruments allow for example the mapping of the distribution of the chemical elements within the region of interest and to analyze the internal structure of the catalytic active centers at nanometer resolution. This often provides all necessary key information to understand the functionality of a catalyst and allows further improving its properties.