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Modification of the Properties of Metal Overlayers oN Nb(110) and Ta(1l0)

  • M. W. Ruckman (a1), Myron Strongin (a1) and Xiaohe Pan (a1)

Abstract

Modification of the physical and chemical properties of noble and near-noble metal monolayer films supported on Nb(110) or Ta(l10) is demonstrated using photoemission and LEED. Strong adlayer-substrate bonding leads to the formation of commensurate Pd or Pt overlayers at low coverage (8 < 0.7 ML). Ni and Cu form incommensurate structures because the additional interfacial misfit cannot be overcome by substrate-overlayer bonding. Ag and Au form commensurate overlayers at coverages le ss than 3 ML because the lattice misfit is small. The strong overlayer-substrate bonding produces large changes in the chemical activity of near-noble metal overlayers. Photoemission measurements on Pt monolayers show that the hybridized metal d-states are shifted further below the Fermi level “EF” and show a reduction in the surface density of states at EF. This absence of bonding d-states near EF effects CO chemisorption. However, as additional layers of Pd and Pt are deposited, the d-occupancy at EF grows, with “constant” atomic structure and the amount of CO increases. Hence, in these systems chemisorption changes can be studied as a function of changing electronic structure while holding the surface structure fixed.

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Modification of the Properties of Metal Overlayers oN Nb(110) and Ta(1l0)

  • M. W. Ruckman (a1), Myron Strongin (a1) and Xiaohe Pan (a1)

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