Potassium adsorption on graphite(0001)
1999 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 420, no 2-3, 174-189 p.Article in journal (Refereed) Published
Potassium adsorption on graphite has been studied with emphasis on the two-dimensional K adlayer below one monolayer. Data are presented for the work function versus coverage, high-resolution electron energy loss spectroscopy (HREELS) vibrational spectra of K-adlayers, low energy electron diffraction and ultraviolet photoemission spectroscopy (UPS) spectra at different coverages. The data provide information regarding the vibrational properties of the K-adlayer, the metallization of the adlayer at submonolayer coverages, and the charge transfer from the It adatoms to the graphite substrate. Analysis of the work function, HREELS, and UPS data provides a qualitatively consistent picture of the charge state of the K adatoms, where at low coverages, below a critical coverage theta(c) (theta(c) = 0.2-0.3), the K adatoms are dispersed and (partially) ionized, whereas at theta > theta(c) islands of a metallic 2 x 2 K phase develop that coexist with the dispersed K adatoms up to theta = 1. We show that it is possible to understand the variation of the work function data based on a two-phase model without invoking a depolarization mechanism of adjacent dipoles, as is normally done for alkali-metal adsorption on metal surfaces. Similarly, the intensity variation as a function of coverage of the energy loss peak at 17 meV observed in HREELS, and the photoemission peak at E-b = 0.5 eV seen in UPS can be understood from a two-phase model. A tentative explanation is presented that connects apparent discrepancies in the literature concerning the electronic structure of the K adlayer. In particular, a new assignment of the K-induced states near the Fermi level is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.
Place, publisher, year, edition, pages
1999. Vol. 420, no 2-3, 174-189 p.
alkali metals, chemisorption, graphite, surface electronic phenomena
Other Physics Topics
IdentifiersURN: urn:nbn:se:uu:diva-235937DOI: 10.1016/S0039-6028(98)00822-XISI: 000078566200009OAI: oai:DiVA.org:uu-235937DiVA: diva2:762464