Potassium adsorption on Ru(0001) at 450 K

The adsorption of potassium on the Ru(0001) surface at 450 K has been studied by LEED, Auger spectroscopy, work function change measurements and neutral atom and ion thermal desorption. The results reveal the existence of a new, ionic desorption peak in the high temperature range and the effects of diffusion of potassium into the bulk at 450 K and above. Work function measurements indicate a dipole-dipole interaction ordering the adiayer over the low coverage range (from θ = 0 toθ = 0.15) and covalent bonding leading to the depolarization of the surface layer at higher coverages ( α = 28 A 3 at θ = 0.37 ). Thermal desorption of ions shows a slight increase in activation energy (from 334 to 343 kJ/mol) for the coverage range studied. LEED results show a series of ordered, commensurate structures formed on the surface starting with the (2 × 2) phase for θ = 0.25 and ( 3 × 3 )R30° for θ=0.33. For higher coverages, a mixed phase consisting of “islands” of ( 3 × 3 )R30° and ( 7 3 × 7 3 ) R±11° structures is observed until the maximum obtainable coverage of 0.37 is reached when the overlayer transforms entirely into a two-domain ( 7 3 × 7 3 ) R±11° pattern.