FIELD DESORPTION AND FIELD EVAPORATION OF METALS

In this review we present adetailed study, both experimental nd theoretical, of the field desorption and field evaporation ofalkali- and transition metals looking in particular at the site specificity and the coverage dependence. A novel experimental pproach based on the retarding potential analysis of metal ions emitted in a continuous field desorption mode is used. With this approach, absolute values of the field ion appearance energy have been measured and binding energies have been obtained for atoms extracted from selected surface sites under high field conditions. We discuss results of the mass-to-charge resolved retarding potential analysis of lithium ions, desorbed from W ( 11 l), and of rhodium ions evaporated from Rh ( 100) and Rh ( 111). Appearance energies of Li+ and Rh2+ were derived from the ion retardation curves, and activation energy data were evaluated from desorption rate measurements. Applying a thermionic ycle, the binding energies of Li adatoms on W ( 111) as well as of Rh at Rh(100) and Rh(ll1) step sites are obtained. The clusrer embedded in jellium model, based on density functional theory, is used to interpret the experimental data. Local field enhancements, binding and activation energies are calculated for Li field desorption and Rh field evaporation as a function of field strength and surface geometry. 1