INTERCALATION OF POTASSIUM FROM THE SURFACE OF GRAPHITE

We have investigated the intercalation of potassium adlayers from the surface of graphite into the bulk. Time-dependent HREELS and LEED data is presented from the submonolayer dispersed phase of potassium on graphite at 50 K, together with HREELS data from a multilayer of potassium on graphite in a range of temperatures from 80 to 220 K. The dispersed phase shows intercalation at 50 K while the multilayer was found to be stable against intercalation up to a temperature of approximately 150 K. This difference is explained in terms of the differing mobilities of the potassium atoms in the two phases; the dispersed phase is fluid whereas the multilayer phase is a solid. The data supports the generally held view that potassium intercalates via the step edges of the graphite layers.