The theory of the workfunction of caesium suboxides and caesium films

Abstract

The lower workfunction of caesium monolayer films compared with that of bulk caesium is explained as a size effect. By the uncertainty principle, confinement to a monolayer raises the electron kinetic energy and hence the Fermi energy leading to an equivalent fall in workfunction. This effect is substantial for alkali metals because of the low density of electrons per atom. A simple calculation is presented to substantiate this claim. The hypothesis that such a size effect is also important in determining the workfunction of the caesium suboxides is proposed. A simple model of the electronic structure of the caesium suboxides is proposed in which they are viewed as composed of regions approximating caesium metal with other regions, occupied by oxygen ions, which are highly repulsive to conduction electrons.