THE WORK FUNCTIONS OF CESIUM ON THE (100) AND (110) ORIENTED FACES OF TUNGSTEN SINGLE CRYSTALS

Abstract

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.