V Production of Electron Probes Using a Field Emission Source

Abstract

This chapter discusses the production of electron probes using a field emission source. Electron probes have a large variety of uses ranging from electron beam evaporators and welders to oscilloscopes, microprobes, and scanning microscopes. These various uses place a variety of different demands upon the electron optical system and upon the electron source itself. By far the majority of these instruments use a hot tungsten filament as the source of electrons because it is simple and easy to use and because it is a well developed technique. It does, however, have its limitations, and therefore the chapter discusses the useful range of the applicability of another source of electrons—field emission—which is superior to the hot filament in brightness but inferior in the total current that can be extracted. It also elaborates the practical features of the process as a source of electrons. A field emission source can be used for the production of electron probes ranging in size from a few Å to a few microns and in energy from a few kV to a few hundred kV.