Photoemission spectroscopy study of a multi-alkali photocathode

In this paper a photoemission study of the highest core levels of the elements and the electron escape barrier (work function) in a multi-alkali photocathode are presented. The core levels indicate that the alkali atoms are in an oxidized state and therefore the compound Na2KSb can be regarded as an ionic semiconductor. The measured escape barrier of the Cs2O surface layer is determined as 2.3 eV.