The influence of oxygen on the desorption kinetics and surface diffusion of potassium on W(112)

Abstract

Using a surface ionization ion microscope the desorption kinetics and the directional dependence of the diffusion of potassium were measured on an oxygen covered W(112) surface at extremely low K-coverages. The mean adsorption lifetime τ can be expressed as τ = 4.8×10 −14 s×exp(2.24 eV/ kT); compared to the clean surface the activation energy of ionic desorption is reduced by 0.3 eV. The oxygen coverage does not change the anisotropy of diffusion observed on the clean surface fundamentally, but slows down the diffusion process. The diffusion constants along the [1̄1̄1] direction (direction of the “channels” on W(112)) and at an angle of 60° relative to it are given by D ∥,ox = 0.9 cm 2 s −1 × exp(−0.60 eV/ kT) and D 60°,ox = 0.2 cm 2 s −1 × exp(−0.72 eV/ kT), respectively.