In a scanning electron microscope (SEM) an electron beam is scanning in a raster pattern over the sample. The electrons interact with atoms in the sample and the secondary electrons emitted by the sample are used to form an image of the sample surface. The SEM at WEMC is a FEI Magellan 400, with an electron energy range from 1 kV to 30 kV and a sub-nanometer resolution (0.8 nm at 15 kV—0.9 nm at 1 kV).
The FEI Magellan 400 is equipped with a Leica cold stage for cryo-microscopy. Low-temperature SEM can be performed on frozen material.
Energy-dispersive X-ray spectroscopy EDX-SEM
During SEM imaging X-rays are emitted from the sample. Interaction of the electron beam with atoms in the sample causes shell transitions which result in the emission of X-rays. An emitted X-ray beam has an energy which is characteristic of the parent element. Determining the emitted X-ray energies can be used for the quantitative elemental analysis of the sample. Energy-dispersive X-ray spectroscopy (EDX) can also be used to form maps or line profiles, showing the elemental distribution in a sample surface (sampling depth 1-2 microns).