Measurement of electric potential distributions around FEG-emitters by electron holography.

An evaluation technique for field emission guns (FEG-emitters) was established by using electron holography. For performing electron holography under an applied voltage, a specimen holder with the capabilities of three-directional motion as well as voltage application was developed. An unused Schottky emitter and a used emitter that had failed after operating for about 10,000 h were selected for this study. By visualizing the electric potential distributions around the emitters, it was clarified that a change in the edge shape of the emitter led to the change in the strength of the electric field. The observations revealed that electron holography can be applied to evaluate the performances of the various emitters.