Abstract: The cathode for photo-electron emission 5 is comprised of an alkali metal containing layer 5d made of material for emitting photo-electrons by the entry of light or for emitting secondary electrons by the entry of electrons, such as particles which consist of an alkali antimony compound, on an Ni electrode substrate 5c on which an Al layer 5b is deposited, and has an intermediate layer 5a made of carbon nano-tubes between the alkali metal containing layer 5d and the Ni electrode substrate 5c, therefore the defect density inside the particles is decreased, and the recombining probability of electrons and holes drops remarkably, which improves the quantum efficiency.

Abstract: A cathode (5) for emitting photoelectrons or secondary electrons comprises a nickel electrode substrate (5c) with an aluminum layer (5b) deposited on it; an intermediate layer (5a) consisting of carbon nanotubes formed on the aluminum layer; and an alkaline metal layer (5d) formed on the intermediate layer (5a) and composed, for example, of particles of an alkali antimony compound that either emits photoelectrons in response to incident light or emits secondary electrons in response to incident electrons. The decrease in defect density of the particles reduces the probability of recombination of electron and hole remarkably, thus increasing quantum efficiency.