The ability to obtain elemental maps in a transmission electron microscope (TEM) or scanning transmission electron microscope (STEM) is extremely useful in the analysis of materials, and semiconductor devices such as ULSI's and GMR heads. Hitachi has developed a new type of elemental mapping system, consisting of a STEM (Hitachi, HD-2000) equipped with a two-window electron energy filter. In-situ calculation of the energy-filtered signal makes it possible to observe real time elemental mapping images with nanometer resolution.

Figure 1 shows a schematic of the elemental mapping system. In the STEM, electrons are generated from a cold field emission gun and accelerated to a potential of 200 kV. The electrons arc focused by the objective lens into a small probe (<1 nm), which is then rastered over the specimen using scanning coils. Transmitted electrons are collected by an energy filter, which is located beneath the specimen., and consists of quadrupole lenses, a magnetic prism spectrometer and two kinds of electron beam energy detectors.