Simultaneous EELS and EDS Acquisition
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EELS and EDS are usually used as complementary analytical techniques in analytical TEMs. By taking the advantages of scanning transmission electron microscope (STEM), high mechanical stability, high brightness probes, fast X-ray and EELS detectors, simultaneous EDS and EELS data acquisition is enabled by allowing each detector system to acquire data independent of the other at spectral rates over 1 kHz with software, e.g. Gatan Digital Micrograph. Gatan generated such a data collection system which is linked together by a synchronization clock pulse to ensure the resulting datasets in exact spatial alignment. The timing precision is reached by hardware-synchronizing the EDS and the EELS spectrometers with the beam scanning system in TEM. During the simultaneous data acquisition, the EELS spectrometer provides system synchronization using a clock pulse at the end of each acquired frame. This pulse is employed to locate the beam position and to inform the EDS system that the pixel has advanced. The EDS and EELS data is stored locally in software buffers. In such simultaneous data acquisition, one can have the benefits of energy dispersive x-ray spectroscopy (EDS) analysis for high-Z elements and of electron energy loss spectroscopy (EELS) for low-Z species at the same time.

However, when they are performed simultaneously, the proper TEM conditions for EELS acquisition are not optimized for EDS because shorter recording times are typically used for EELS. Therefore, when doing simultaneous EDS and EELS mapping, a compromise must be figured out to have a long enough time for a good EDS intensity and short enough so as not to saturate the EELS CCD detector.

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