THE SURFACE-STRUCTURE OF A C(2 X-2) POTASSIUM OVERLAYER ON CO(1010)

CJ BARNES*, P HU, M LINDROOS, DA KING

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The surface structure of the clean Co{1010BAR} surface and a c(2 x 2) potassium overlayer have been determined by quantitative low energy electron diffraction. The Co{1010BAR} sample has been shown to be laterally unreconstructed with the surface being uniquely terminated by an outermost closely packed double layer (dz12 = 0.68 angstrom). A damped oscillatory relaxation of the outermost three atomic layers occurs, with relaxations DELTA-dz12 = -6.5 +/- 2% and DELTA-dz23 = +1.0 +/- 2%.

The c(2 x 2) overlayer formed at a coverage of 0.5 ML was subjected to a full I-V analysis. A range of adsorption sites were tested including fourfold hollow, on-top, and both long and short bridge sites in combination with both "long" and "short" cobalt interlayer terminations. A clear preference was found for adsorption in the maximal coordination fourfold hollow site. No switching of surface termination occurs. The potassium adatoms reside in the [1210BAR] surface channels directly above second layer cobalt atoms with a potassium to outermost cobalt interlayer separation of 2.44 +/- 0.05 angstrom. Potassium-cobalt bond lengths of 3.40 +/- 0.05 and 3.12 +/- 0.05 angstrom between the four (one) outermost (second) layer nearest-neighbour substrate atoms suggests a potassium effective radius of 1.87 +/- 0.05 angstrom, somewhat smaller than the Pauling covalent radius and considerably larger than the ionic radius (1.38 angstrom). The alkali-surface bonding is thus predominantly "covalent"/"metallic".

Original languageEnglish
Pages (from-to)561-567
Number of pages7
JournalSurface Science
Volume251
Publication statusPublished - Jul 1991
Event11TH EUROPEAN CONF ON SURFACE SCIENCE ( ECOSS-11 ) - SALAMANCA, Spain
Duration: 01 Oct 199004 Oct 1990

Keywords

  • ENERGY ELECTRON-DIFFRACTION
  • LEED
  • RELAXATION
  • NI(001)
  • NA

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