We report a theoretical investigation of the adsorption of alkali metal atoms deposited on ultrathin oxide films. The properties of Li, Na, and K atoms adsorbed on SiO(2)/Mo(112) and of K on MgO/Ag(100) and TiO(2)/Pt(111) have been analyzed with particular attention to the induced changes in the work function of the system, Phi. On the nonreducible SiO(2) and MgO oxide films there is a net transfer of the outer ns electron of the alkali atom to the metal substrate conduction band; the resulting surface dipole substantially lowers Phi. The change in Phi depends (a) on the adsorption site (above the oxide film or at the interface) and (b) on the alkali metal coverage. Deposition of K on reducible TiO(2) oxide films results in adsorbed K(+) ions and in the formation of Ti(3+) ions. No charge transfer to the metal substrate is observed but also in this case the surface dipole resulting from the K-TiO(2) charge transfer has the effect to considerably reduce the work function of the system. (C) 2008 American Institute of Physics.

Martinez, U., Giordano, L., Pacchioni, G. (2008). Tuning the work function of ultrathin oxide films on metals by adsorption of alkali atoms. THE JOURNAL OF CHEMICAL PHYSICS, 128(16) [10.1063/1.2905218].

Tuning the work function of ultrathin oxide films on metals by adsorption of alkali atoms

GIORDANO, LIVIA;PACCHIONI, GIANFRANCO
2008

Abstract

We report a theoretical investigation of the adsorption of alkali metal atoms deposited on ultrathin oxide films. The properties of Li, Na, and K atoms adsorbed on SiO(2)/Mo(112) and of K on MgO/Ag(100) and TiO(2)/Pt(111) have been analyzed with particular attention to the induced changes in the work function of the system, Phi. On the nonreducible SiO(2) and MgO oxide films there is a net transfer of the outer ns electron of the alkali atom to the metal substrate conduction band; the resulting surface dipole substantially lowers Phi. The change in Phi depends (a) on the adsorption site (above the oxide film or at the interface) and (b) on the alkali metal coverage. Deposition of K on reducible TiO(2) oxide films results in adsorbed K(+) ions and in the formation of Ti(3+) ions. No charge transfer to the metal substrate is observed but also in this case the surface dipole resulting from the K-TiO(2) charge transfer has the effect to considerably reduce the work function of the system. (C) 2008 American Institute of Physics.
Articolo in rivista - Articolo scientifico
oxide surfaces, DFT
English
2008
128
16
164707
none
Martinez, U., Giordano, L., Pacchioni, G. (2008). Tuning the work function of ultrathin oxide films on metals by adsorption of alkali atoms. THE JOURNAL OF CHEMICAL PHYSICS, 128(16) [10.1063/1.2905218].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/45151
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