Surface diffusion of potassium on (100) and (111) germanium planes

Abstract

Surface diffusion of potassium on atomically clean (100) and (111) germanium single crystal planes has been investigated by means of the field emission method. Sealed-off field emission tubes with a channel multiplier were used. The surface density of potassium adatoms on the germanium surface was determined by using a standard tungsten crystal plate, movable between the adsorbate atom flux and a low-energy electron gun. The influence of the external electric field on the surface diffusion of potassium has been studied with the aim to determine the dipole moment of the potassium adatoms on the germanium surface. The obtained values of 4.5 ± 0.2 and 4.1 ± 0.2 debye for potassium adatoms on (100) and (111) germanium planes, respectively, are in good agreement with initial dipole moments calculated from work function measurements. The influence of the atomic relief and the electronic structure of the substrate on the properties of an alkali adlayer on a semiconductor surface is discussed on the basis of experimental results.