Field emission type electron source and method of making same

Abstract

An electron source includes a cathode electrode having an emitter of conical shape. A first insulating film surrounds the emitter. A first extracting electrode disposed on the first insulating film draws out electrons from the emitter. A second insulating film is disposed on the extracting electrode and a focusing electrode is disposed on the second insulating film for focusing the electrons. The films and electrodes are hollowed to constitute a well surrounding the emitter, and the electrodes are applied predetermined voltages respectively to control the electrons emitted from the emitter. A disturbance that the voltage applied to the focusing electrode causes to the electric field around a summit of the emitter is suppressed. The electrode source may be made by determining a thickness of a masking material so that, when forming the conical emitter, an area occupied by the films deposited on the masking material in the well is smaller than the well when all the films have been completed. The emitter of conical shape is formed in the cathode electrode by using the mask having the determined thickness. The first insulating film, the extracting electrode, the second insulating film, and the focusing electrode are then successively formed, after removing the mask and the layers deposited on the mask successively.