New Approach to Obtain Elemental Maps by Using Energy-Filterd Images
Microscopy and Microanalysis
The ability to obtain elemental maps processed by using inelastically scattered electrons in a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) is extremely useful in the analysis of materials, and semiconductor devices such as ULSI's and GMR heads. Hitachi developed an elemental mapping system, consisting of a STEM (Hitachi, HD-2000) equipped with a two-window energy filter (Hitachi, ELV-2000), and performed real-time conventional jump-ratio images
... jump-ratio images with nanometer resolution by in-situ calculation of energy-filtered signals . Since images can be obtained by only one-scan of the electron beam on the specimen, no artifacts due to sample-drift appear. But it is problem that artifacts in jump-ratio images due to the difference of inclination in EEL (Electron Energy-Loss) spectra will give incorrect information when investigating elemental maps. For example, heavy elements such as tungsten (W) often show bright contrast as artifacts in light elemental jump-ratio images such as nitrogen and oxygen. On the other hand, it is possible to obtain the quantitative elemental maps by using 3-window method. In this paper, we propose new approach to obtain elemental maps without artifacts due to heavy elements.