EELS: A tool for investigating biological materials

Electron energy loss spectroscopy (EELS) is the analysis of the energy distribution of the electrons that have passed through a thin sample and have interacted with it inelastically. EELS is a very powerful technique capable of providing chemical and electronic information from particular areas in the sample. Spatial information can be obtained using two approaches: the first method is to combine EELS with a scanning transmission electron microscope (STEM) where the electron probe is scanned across a selected area in the sample and an EELS spectrum is collected point by point across the scan giving a spectrum image (SI). The second method is to use energy-filtered transmission electron microscopy (EFTEM). EFTEM utilizes a special spectrometer which has the capability to filter the energy of the electrons that have interacted with the specimen. Concentrating on a particular ionization edge it is possible to build up images which show a two dimensional distribution of a particular element.

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