Metallurgical applications of scanning transmission electron microscopy

It is shown that scanning transmission electron microscopy (STEM) has followed two main lines of development, the pure STEM based upon a field emission electron source in which the emphasis is given to high resolution, and a combined system in which STEM is an attachment to a conventional transmission microscope (TEM + STEM). When used in combination with an energy dispersive X-ray spectrometer, the combined TEM + STEM system is shown to be extremely versatile and possibly the more useful for the applied metallurgist. The high vacuum requirements of pure STEM, however, make this system suitable to be used in conjunction with an Auger spectrometer. Examples of the various microanalysis facilities of STEM are given in the article, including microdiffraction, rocking-beam channeling patterns, qualitative and quantitative X-ray spectroscopy analysis, particle analysis and in-situ experimentation. The controversial subject of whether thicker specimens can be studied in STEM compared with conventional TEM is also discussed.