CESIUM ADSORPRION ON INSULATING SUBSTRATES

Theoretical and experimental results are presented which clarify the nature of thin cesium layers adsorbed on insulating substrates. From a consideration of the forces acting on adsorbed Cs atoms and ions, it is found that the Cs is adsorbed in atomic form. A model based on image-force considerations predicts the ionization energy of the isolated adsorbed atom to be about 1.4 eV, and the corresponding dipole moment to be about 3 D units directed toward the substrate. As the surface coverage increases, adsorbate interactions produce an increasing ionization energy. Photoemission threshold measurements indicate that the surface coverage on a clean, smooth surface is about one monolayer for a system in thermal equilibrium with a Cs reservoir. © 1968 The American Institute of Physics.