Coverage dependence of the electronic structure of potassium adatoms on the Si(001)-(2 times 1) surface

Journal Article · Fri Dec 15 04:00:00 EST 1989 · Physical Review (Section) B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.40.11519· OSTI ID:7168279

Ishida, H; Terakura, K ^[1]

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1. Institute for Solid State Physics, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, (Japan)

The electronic structure of potassium adatoms on the Si(001)-(2{times}1) surface is studied by first-principles calculations within the local-density-functional theory for a wide range of the K coverage ({Theta}) including low {Theta} values with negligibly small direct interactions among adatoms. The symmetric dimer model is assumed for the substrate Si which is modeled by a ten-layer slab. As possible adsorption sites for K, a raised site on the Si dimer chain and/or a valley site between two dimer chains are considered. The calculations are performed for {Theta} ranging from 1/6 to 1 in units of Si monolayers including the Levine model ({Theta}=(1/2)) and also recently proposed double-layer model ({Theta}=1). No free-electron-like surface band characteristic of the K 4{ital s} state appears in the Si gap even for higher {Theta}. However, the two gap states originating from the Si dangling bonds in the limit of {Theta}{r arrow}0 shift to higher binding energies by {similar to}0.5 eV with increasing {Theta} due to the kinetic energy lowering caused by the delocalization of their wave functions toward the overlayer. This is interpreted as a result of the Si-K hybridization which leads to the polarized covalent Si-K bond. The adatom region is essentially neutral even for lower {Theta} if the charge density is averaged in a K sphere, which implies that the adatom-induced dipole moment to reduce the work function shold be attributed to the adatom polarization due to the Si-K orbital mixing rather than the conventional {Theta}-dependent charge transfer.

• OSTI ID: 7168279
• Journal Information: Physical Review (Section) B: Condensed Matter; (USA), Journal Name: Physical Review (Section) B: Condensed Matter; (USA) Vol. 40:17; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ADSORPTION
ALKALI METALS
BINDING ENERGY
CHARGE TRANSPORT
DIPOLE MOMENTS
ELECTRONIC STRUCTURE
ELEMENTS
ENERGY
METALS
POTASSIUM
SEMIMETALS
SILICON
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES