Emitters for Fine Electron Probes

Abstract

Modern electron microscopes are usually provided with a field emission (FE) electron gun (FEG) using a W <310> cold FE emitter or ZrO/W thermal FE emitter. Also, an LaB 6 thermionic emitter is widely used for high-brightness electron guns for electron beam instruments such as electron microscopes (EM) and Auger electron spectrometers (AES). The LaB 6 emitter can work well in a high vacuum of the 10 −5 Pa range.The ZrO/W emitter is classified as a Schottky emission type, although the emitter is generally recognized as a thermal FE emitter. The ZrO/W emitter can work in the 10 −7 Pa range, and the W <310> emitter works in the 10 −8 Pa range. The W <310> emitter produces the smallest spot size among these emitters. The ZrO/W Schottky emission (SE) emitter can emit a higher current than the W <310> emitter.