Coadsorption of Li and Na on Al(100)

• Published in: Surface science Vol. 461; no. 1; pp. 45 - 53
• Main Authors: Petersen, J.H., Søndergård, C., Hoffmann, S.V., Adams, D.L.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.08.2000; Amsterdam Elsevier Science; New York, NY
• Subjects: Adsorbed layers and thin films; Adsorption and desorption kinetics; evaporation and condensation; Alkali metals; Aluminum; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Low energy electron diffraction (LEED); Photoelectron spectroscopy; Photoemission (total yield); Photoemission and photoelectron spectra; Physics; Solid surfaces and solid-solid interfaces; Solid-fluid interfaces; Surface structure and topography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Low energy electron diffraction (LEED); Aluminum; Photoelectron spectroscopy; Alkali metals; Photoemission (total yield); Sodium; Coadsorption; Adsorption structure; Lithium; Aluminium; LEED; Experimental study
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(00)00489-1

The coadsorption of Li and Na on Al(100) has been studied by high-resolution core-level spectroscopy and low energy electron diffraction. Coadsorption of 0.25 ML Li and 0.25 ML Na at room temperature leads to the formation of a c(2×2) structure, which is shown to be a substitutional surface ternary alloy, in which the alkali atoms randomly occupy the vacancies in a c(2×2)-Al sublattice. Adsorption of 0.5 ML Li followed by 0.5 ML Na at room temperature leads again to the formation of a c(2×2) structure. This is shown to be a multilayer surface ternary alloy, consisting of a mixed c(2×2)-Al/Na layer, followed by a (1×1)-Al layer, followed by a mixed c(2×2)-Al/Li layer. This structure is also obtained by reversing the adsorption sequence. Adsorption of 0.5 ML Li at room temperature followed by 0.5 ML Na at 120 K leads again to the formation of a c(2×2) structure, which consists of a chemisorbed Na overlayer on a mixed c(2×2)-Al/Li layer. Surprisingly, reversing the adsorption sequence leads again to the same structure. The mechanisms of formation of the different phases are discussed.