Modification of the properties of metal overlayers on Nb(110) and Ta(110)
Modification of the physical and chemical properties of noble and near-noble metal monolayer films supported on Nb(110) and Ta(110) is demonstrated using photoemission and LEED. Strong adlayer-substrate bonding leads to the formation of two-dimensional coherent Pd or Pt overlayers at low coverage (theta < 0.7 ML). Ni and Cu form one-dimensional coherent structures because the additional interfacial misfit cannot be overcome by substrate-overlayer bonding. In the case of Ag and Au overlayers, slightly strained pseudomorphic structures are formed 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 ''E/sub F/'' and show a reduction in the surface density of states at E/sub F/. This absence of bonding d-states near E/sub F/ effects CO chemisorption. However, as additional layers of Pd and Pt are deposited, the d-occupancy at E/sub F/ 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.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA); Queens Coll., New York (USA). Dept. of Physics
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 7123040
- Report Number(s):
- BNL-39096; CONF-861207-44; ON: DE87004606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104* -- Metals & Alloys-- Physical Properties
ADSORPTION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
COHERENT SCATTERING
COPPER
D STATES
DEPOSITION
DIFFRACTION
ELECTRON DIFFRACTION
ELEMENTS
EMISSION
ENERGY LEVELS
FILMS
FUNCTIONS
GOLD
LAYERS
METALS
NICKEL
NIOBIUM
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PHOTOEMISSION
PLATINUM
PLATINUM METALS
SCATTERING
SECONDARY EMISSION
SEPARATION PROCESSES
SILVER
SORPTION
SORPTIVE PROPERTIES
SPECTRA
SUBSTRATES
SURFACE COATING
SURFACE PROPERTIES
TANTALUM
TRANSITION ELEMENTS
WORK FUNCTIONS