ABSTRACT
The scanning electron microscope (SEM) is extensively used in many fields of research and industrial production throughout the world. The SEM provides higher spatial resolution analysis and inspection than that afforded by current techniques using the optical microscopes. Owing to recent developments, especially in variable vacuum instrumentation, the SEM is used in research, development, and production where previously excessive sample charging and damage limited its use. There are two basic categories of point cathode electron source types used in the current SEMs: cold field emission and thermally assisted field emission cathodes. The configuration of the low-vacuum SEM column is about maintaining the electron gun and column at high vacuum and the specimen region at low-vacuum values while providing a transition region between them. Beyond the spatial resolution or focusing ability of the system it is also essential to avoid electron beam induced contamination, which until is one of the most bothersome problems of the SEM.
