Abstract
The effect of low-energy ion bombardment on the surface structure of Ag(111) and on the reactivity towards oxygen has been investigated by ellipsometry and LEED. Bombardments were carried out with argon ions with energies between 200 and 550 eV and at current densities of 0.33 to 2.0 micro A/cm 2 . The ellipsometric parameters, Δ and ψ, increase during the removal of an adsorbed layer and decrease upon prolonged bombardment. The first fast decrease at the start of the bombardment of a clean surface is ascribed to argon implantation and the subsequent slower and finally constant rates of change of Δ and ψ to the formation of clusters of vacancies and interstitials in a thin (∼100 Å) layer at the surface. The highest change in Δ amounted to 10°, as yet without an indication to reach a limiting value. The LEED pattern of a heavily bombarded surface is not much different from that of an annealed surface. The optical constants calculated for the damaged layer correspond to those of unannealed thin films. The number of defects introduced per incident ion is estimated at 10 −3. According to ellipsometry complete recovery of the damaged surface takes place at 250°C. The amount of oxygen adsorbed on a completely annealed surface is small and increases with increasing damage.
Published Version
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