Cathode for photoelectric emission, cathode for secondary electron emission, electron multiplier tube, and photomultiplier tube

摘要

A cathode for photoelectric emission or a cathode for secondary electron emission comprises a thin film made of a material which emits photoelectrons by an incident light or emits secondary electrons by an electron input on a base substrate. The average particle size of the particles forming the thin film is 200 nm to 2000 nm. It is preferred that the average particle size is nearly equal to an average diffusion length of the particle of an excited electron. Further, the average particle size is preferably larger than the mean value of penetration lengths of inputted electrons or incident lights in the particles. Moreover, preferably convexities and/or concavities formed of particles each having the average particle size are formed over the surface of a plane for the incident light or electron input. Further, it is preferred that the thin film is activated by an alkali metal and is made of compounds of at least one kind of alkali metal and an antimony metal. Moreover, a layer having high reflectance against light is preferably inserted between the base substrate and the thin film. Thus, according to the cathode for photoelectric emission or the cathode for secondary electron emission, photoelectrons or secondary electrons are generated effectively and emitted from the cathode for photoelectric emission or the cathode for secondary electron emission.