The Work Functions of Cesium on the (100) and (110) Oriented Faces of Tungsten Single Crystals

Work-function measurements have been made at room temperature, using the vibrating capacitor technique, on (110) and (100) oriented tungsten single-crystal surfaces both clean and covered with cesium. After complete cesiation the work functions of the two surfaces were, respectively, 2.06 ± 0.01 eV and 1.82 ± 0.01 eV. On the basis of a model involving epitaxial growth of the cesium and a doubling of the lattice constant, the work-function differences between the two surfaces, clean and cesiated, are found to agree well with the predictions of Smoluchowski. Comparison of the present result on the (110) plane, covered with a monolayer of cesium, with a published value for a thick film of cesium indicates that there may be very little contribution to the work function from atoms in the solid other than those in the outermost atomic layer.