An Analytical Scanning Transmission Electron Microscope

A scanning transmission electron microscope (STEM) with a field emission gun has been developed for quantitative microanalysis. The high brightness source combined with X-ray analysis, electron diffraction and electron energy loss analysis provides a technique of microanalysis from regions of thin specimens as small as a few hundred angstroms. The electron optical lay-out of this microscope is shown in Figure 1. A triode field-emission gun is mounted in a U HV chamber with mu-metal walls for screening. The gun which can be operated at up to 100kV provides a virtual source; the position of this source is largely independent of the ratio of the acceleration voltage to extraction voltage.