Red sensitive photocathode having an aluminum oxide barrier layer

Abstract

In a photomultiplier tube, antimony layers of a photocathode are prepared on a nickel substrate by providing a barrier layer of aluminum oxide between the substrate and antimony layers. The photocathode is subsequently exposed to the vapors of at least one alkali metal to sensitize the antimony layers. The aluminum oxide layer prevents alloying of the nickel with the antimony at processing temperatures in the range from 260.degree. C. to 285.degree. C. and provides a source of oxygen to oxidize the photocathode for increased photosensitivity, the oxidation time being a function of the thickness of the aluminum oxide layer. The photocathode is then exposed to cesium and may be superficially oxidized until substantially maximum photosensitivity is achieved.

Dependencies are inferred from the claim text.