Electron Microscopy

Electron Microscopy

We use transmission electron microscopy (TEM) to investigate the atomic structure and composition of nanomaterials. In the high-resolution TEM (HRTEM) mode the whole region of interest of our specimen is illuminated with the electron beam and the image is formed with the objective lens and further magnifying lenses. In the Scanning TEM (STEM) mode, the electron beam is focused to a diameter down to 50 pm. The focused beam is scanned over the specimen and scattered electrons are detected with different detectors. Images are formed by plotting the detector signal at each scan position.  The composition of the specimen is measured with energy dispersive X-ray analysis (EDX) and energy loss spectroscopy (EELS). Electron tomography yields the 3D structure of our specimen.

What kind of result do I get?

The high-resolution TEM and STEM images show the atomic structure of the specimen projected along the electron beam direction. The images reveal the crystal structure, dislocations and stacking faults. The positions of atom columns are measured with an accuracy of a few picometers. Distances between atom columns give information on the strain distribution in our specimen. In the STEM mode, using the high-angle annular dark field (HAADF) detector, the brightness of an atom column increases with the atomic number, so that we can distinguish different elements in the images. An atom hit by the electron beam emits a characteristic X-ray spectrum. Its measurement in STEM allows 2D elemental mapping, detecting elements even at small concentrations below 1%.

Application Scientist

Dr. Marco Schowalter

MAPEX Center for Materials and Processes
University of Bremen

Otto-Hahn Allee 1, D-28359 Bremen
Phone: +49 421 218 62263
Email: schowalter@ifp.uni-bremen.de

Dr. Thorsten Mehrtens

MAPEX Center for Materials and Processes
University of Bremen

Otto-Hahn Allee 1, D-28359 Bremen
Phone: +49 421 218 62273
Email: mehrtensprotect me ?!ifp.uni-bremenprotect me ?!.de