Coadsorption of Beryllium and Potassium on a (001) Tungsten Plane

The adsorption and coadsorption of beryllium and potassium on the tungsten (001) plane was studied using a probe-hole field electron microscope (FEM). Measurements were made at 78 K for potassium and at 300 K for beryllium. It has been found that the adsorption of potassium decreases and that of beryllium increases the work function of the W(001) plane. At small coverages with potassium atoms (θ$\text{}_{k}$ < 0.2) on the W(001) plane successive evaporation of beryllium atoms causes a decrease of the work function. At larger coverages with potassium atoms an opposite effect is observed. An attempt has been made to compare the experimental results with the theoretical models suggested recently.