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 photoelect ron emission microscopy (PEEM). It is shown that the method can be use d to investigate diffusion in the full monolayer coverage region by ca librating brightness versus coverage in the PEEM image. In addition to a very fast diffusion stage at the lowest concentrations (< 0.05 mono layer (ML)), a local maximum in the diffusion coefficient at 0.5 ML wa s identified and correlated with the formation of the ordered (2 x 2) phase.