SURFACE DIFFUSION IN COADSORBED LAYERS WITH DIFFERENT MOBILITIES OF ADSORBATES:(Li +Dy) ON Mo(112) AND (Li+Sr) ON W(112)

摘要

With the aim to study the regularities of surface diffusion in coadsorbed layers, we investigated diffusion of lithium on the (112) surfaces of Mo and W precovered with submonolayers of dysprosium and strontium, which have substantially lower mobilities than lithium. Experiments were carried out using scanning contact-potential microscopy, and Li diffusion parameters were extracted from diffusional evolution of coverage profiles. Dy and Sr preadsorbed in amounts of ～10~(-1) of a monolayer were found to reduce the diffusion rate of Li by orders of magnitude. The strong impact of coadsorbates with low mobility on Li diffusion can be caused by important role of collective mechanisms in surface diffusion, which entails pronounced pinning effects, as well as by the possibility of formation of surface alloys and surface vitrification.