Structure and formation of surface alloys by adsorption of Li on Al(1 1 0)

The surface structures formed by the adsorption of Li on Al(1 1 0) at room temperature have been studied by low energy electron diffraction (LEED) and core-level photoemission spectroscopy (CLS). The Al(1 1 0)–c(2×2)-Li structure formed by adsorption of one-half monolayer (ML) Li is shown by analysis of extensive LEED measurements to be an ordered surface alloy. The structure contains Li atoms in two-fold substitutional sites formed by the displacement of 0.5 ML Al atoms from the first layer of the substrate. This reconstructive adsorption leads to strong perturbations of the substrate extending five layers into the solid. CLS measurements provide insight to the adsorption geometry at coverages below and above 0.5 ML Li. In particular, it is found that adsorption of Li at coverages above 0.5 ML leads to the formation of a partially disordered, multilayer surface alloy.