ABSTRACT

In principle, scanning transmission electron microscopy (STEM) is a very straightforward technique: a fine electron probe is scanned across a thin specimen and the intensity of the transmitted electron signal is measured using one or more electron detectors. STEM instruments tend to cost more than transmission electron microscopy (TEM) instruments because there are ultra-high vacuum requirements, additional components in the microscope, and extra electronics to drive them. One advantage of STEM is the ease of interfacing to a computer, since by its very nature a STEM is an electronic microscope. High direct magnification TEM images are sometimes only dimly visible on the phosphor screen and they often have only limited contrast; in STEM the image stays bright even at the highest magnifications and contrast can be adjusted electronically. It is usual to conduct TEM experiments in a darkened room, but with a STEM one normally only dims the lights for comfort.