COVERAGE-DEPENDENT SURFACE-DIFFUSION OF K ON PD(111) STUDIED WITH PHOTOELECTRON EMISSION MICROSCOPY

The surface diffusion of K on Pd{111} has been studied with photoelectron emission microscopy (PEEM). It is shown that the method can be used to investigate diffusion in the full monolayer coverage region by calibrating brightness versus coverage in the PEEM image. In addition to a very fast diffusion stage at the lowest concentrations (< 0.05 monolayer (ML)), a local maximum in the diffusion coefficient at 0.5 ML was identified and correlated with the formation of the ordered (2 x 2) phase.