Field desorption of caesium and barium from graphen nanoclueters on the iridium surfaces

Abstract

The features of the field desorption of caesium and barium from the surface of an iridium tip with two-dimensional graphene nanoclusters on the surface are investigated. Both adsorbates are located both on the surface of iridium and carbon clusters, and in the intercalated state under the graphene film in the close packed planes of the iridium crystal. Field desorption proceeds in different ways. With an increase in the intensity of the applied electric field, the pulse removal of the adsorbate from the surface occurs. With further strengthening of the field in the case of caesium, desorption of adsorbate atoms from the intercalated state occurs. Caesium atoms come out from under the film, diffuse onto the surface of the cluster and are desorbed in the ion form. Barium atoms remain under the graphene film until the cluster is destroyed. The difference in the mechanisms of field desorption from graphene clusters is explained by the presence of a second electron on the valence shell of alkali metal atoms, which provides a chemical bond between the adsorbed atoms and the substrate. The only valence electron of alkali metal atoms during adsorption goes into the metal, and provides an electrostatic bond of the adsorbate with the substrate and electrostatic repulsion of the adatoms among themselves.

Keywords

• field desorption
• clusters
• carbon
• iridium
• caesium
• barium