Photoelectric Emission from Thin Films of Caesium

The photoelectric properties and the methods of preparing thin films of caesium are described. These are divided into two classes: (1) Those where a thin film of Cs is adsorbed on a thin layer of oxygen. (2) Those where a thin film of Cs is adsorbed on a layer of suboxides of Cs.Surfaces of the latter type were prepared by coating a cathode with metallic caesium and then admitting oxygen in very small quantities. The photoelectric current was observed simultaneously. The measurements show that the most sensitive surfaces are obtained when the caesium has taken up sufficient oxygen to form a suboxide rather than the normal oxide Cs₂O. These films owe their properties to the arrangement of the molecules very near the surface.