Metal--metal bonding on surfaces: Zn--Au on Ru(001)

Journal Article · Tue Dec 15 04:00:00 EST 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.463318· OSTI ID:7051651

Rodriguez, J A; Hrbek, J ^[1]

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1. Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

The properties of Zn, Au, and Zn--Au films on Ru(001) have been studied using thermal desorption mass spectroscopy (TDS) and core and valence-level photoemission. TDS spectra show desorption of Zn from Ru(001) at 450 (multilayer), 490 (second layer), and 720 K (first layer). The monolayer of Zn desorbs following zero-order kinetics with an activation energy for desorption of 36 kcal/mol. Photoemission studies show that the Zn(3{ital s}) and Zn(3{ital d}) levels of Zn bonded to Ru are shifted 0.5 eV toward lower binding energy with respect to the corresponding levels of pure metallic Zn. The direction of this binding-energy shift together with the results of CO-TDS indicate that Zn is withdrawing electrons from the Ru(001) surface. Such charge transfer is in part responsible for the large stability of the Ru--Zn bond. Au desorbs from Ru(001) at temperatures of 1175 (multilayer) and 1260 K (first layer). For a monolayer of Au deposited on Ru(001), the positions of the Au(4{ital f} ) and Au(5{ital d}) levels are very close to those of the surface atoms of Au(111), indicating that charge transfer between Au and Ru is minimal. A comparison of the desorption temperature for a monolayer of Zn or Au from Ru(001) with values previously reported for the desorption of monolayers of alkali (K and Cs), noble (Cu and Ag), and transition (Mn, Ni, and Pd) metals indicates that the strength of a metal--metal bond in a bimetallic surface depends on (1) the bulk cohesive energy of the individual metals (which gives an indication of the tendency of the element to form strong metal--metal bonds), and (2) the charge transfer within the bond. Zn and Au alloy when coadsorbed on Ru(001). Results for submonolayer coverages of Zn and Au show that the Zn--Ru and Zn--Au bonds in the trimetallic system are more stable than the corresponding bonds in Zn/Ru(001) or Zn--Au alloys.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7051651
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 97:12; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360104 -- Metals & Alloys-- Physical Properties
ACTIVATION ENERGY
ALLOYS
BINDING ENERGY
CHARGE EXCHANGE
CHEMICAL BONDS
CHEMISTRY
DESORPTION
ELECTRONIC STRUCTURE
ELEMENTS
ENERGY
FILMS
GOLD
GOLD ALLOYS
MASS SPECTRA
METALS
PLATINUM METALS
RUTHENIUM
SORPTION
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
TRANSITION ELEMENTS
ZINC
ZINC ALLOYS