ELECTRON SPECTROSCOPIC MICROSCOPY IN MATERIALS SCIENCE

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We investigated performance and applicability of the new energy filtering transmission electron microscope which was recently installed in Kyushu University (KU), and compared with those of microscopes in Max-Planck Institute and Arizona State University. The new microscope in KU has a field emission gun of Shottcky type and an imaging filter of omega-type. The imaging energy spectrometer enables us to use the information included in the inelastically scattered electrons and to improve the contrasts of magnified images as well as diffraction patterns.(1) Electron spectroscopic imaging : By changing a position and a width of energy selecting slit, we can select the energy of electrons to be used for imaging. The contrasts of filtered zero-loss images are improved in the multi-beam resolution images as well as bright-field or dark-field images, although the size and position of an objective apertureare are different in these imaging modes. Images of coherent precipitates, stacking faults and dislocations in metals and alloys are sharp in filtered zero-loss images. The effect of energy filtering is pronounced in thicker spsecimen and lower accelerating voltage. A filtered core-loss (inner-shell ionization) image includes information on composition of a particular element in material (element mapping). Thin oxide layer in Si water is visualized in a two-dimensional scale in the filtered K-loss oxygen image.(2) Electron spectroscopic diffraction : Energy filtered diffraction patterns are obtained by changing the energy slit in the diffraction mode. Inelastically scattered electrons are responsible for the background in diffraction patterns. The background is well eliminated and contrast is much improved in the zero-loss filtered diffraction patterns. We can observe weak diffraction spots or diffuse maxima in the selected-area diffraction patters, and weak diffraction lines of a higher order Laue zone in convergent electron diffraction patters.