Field emission SEM with wide operating voltage range

Abstract

A newly developed conical anode field emission electron gun (FE-GUN)has been installed on the JSM-840F Scanning Electron Microscope (SEM). The cross sectional view of the column is shown in Fig. 1. The gun is usable at a wide accelerating voltage range from 0.5 kV to 40 kV, and is suitable for general purpose SEMs. The gun can be used within the virtual source range even at an extract voltage as high as 7 kV and an accelerating voltage as low as 0.5 kV. The extract voltage can be raised up to 7 kV even when the emitter tip radius becomes larger after repeated flashing for smoothing the emitter tip surface. This allows elongation of the emitter life.With the FE-GUN, since the electron source (virtual source) moves with accelerating voltage change, an image may disappear due to the deviation of the electron probe from the optical axis when the accelerating voltage is changed.