FIELD DESORPTION AND FIELD EVAPORATION OF METALS

In this review we present a detailed study, both experimental and theo retical, of the field desorption and field evaporation of alkali- and transition metals looking in particular at the site specificity and th e coverage dependence. A novel experimental approach based on the reta rding potential analysis of metal ions emitted in a continuous field d esorption mode is used. With this approach, absolute values of the fie ld ion appearance energy have been measured and binding energies have been obtained for atoms extracted from selected surface sites under hi gh field conditions. We discuss results of the mass-to-charge resolved retarding potential analysis of lithium ions, desorbed from W(111), a nd of rhodium ions evaporated from Rh(100) and Rh(111). Appearance ene rgies of Li+ and Rh2+ were derived from the ion retardation curves, an d activation energy data were evaluated from desorption rate measureme nts. Applying a thermionic cycle, the binding energies of Li adatoms o n W(111) as well as of Rh at Rh(100) and Rh(111) step sites are obtain ed. The cluster embedded in jellium model, based on density functional theory, is used to interpret the experimental data. Local field enhan cements, binding and activation energies are calculated for Li field d esorption and Rh field evaporation as a function of field strength and surface geometry.