Photocathode having ultra-thin protective layer

摘要

PURPOSE: A photocathode with an extremely thin protective film is provided to simplify processes, reduce costs and allow for ease of manufacture of device using a photocathode with a large area, by permitting processes to be freely performed in the atmosphere after the evaporation of photoelectric surface. CONSTITUTION: A photocathode comprises a transparent substrate(21); a photoelectric surface(24) evaporated on the transparent substrate, and which converts the light incident through the transparent substrate into electrons and emits electrons; a first photoelectric surface protective film(25) for covering the photoelectric surface and protecting the photoelectric surface from atmosphere; a transparent conductive plate(22) interposed between the transparent substrate and the photoelectric surface; and a second photoelectric substrate(23) interposed between the transparent conductive plate and the photoelectric surface. The electrons emitted from the photoelectric surface pass through the first photoelectric surface protective film by tunneling effects.