Removable organic protective coating for alkali-antimonide photocathodes

We describe a technique for protecting alkali-antimonide visible light photocathodes against deterioration by exposure to impurities, during handling or storage in poor vacuum or gas. The photocathodes are coated with a ∼1 μm vacuum-deposited hexatriacontane film, which can be subsequently removed by low-temperature sublimation. We show that Cs3Sb coated photocathodes can be exposed for several minutes to considerable amounts of oxygen, without deterioration. Their initial photoemission properties are almost fully recovered after film removal.