Photoemission studies of the electronic structure of selected metal overlayers on Ta(110) and their effect on chemisorption

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5792085

Ruckman, M W

Photoemission spectroscopy and conventional surface science analytical techniques have been utilized to study the electronic structure of ultra-thin Ni, Pd, and Pt layers on Ta(110). Of great interest is the fact that the chemical properties of the overlayers differ from the bulk properties of either the substrate or the overlayer metal, and part of this work was designed to understand the origin of this difference. Photoemission studies showed that for initial coverage, each overlayer metal had its d-band moved below E/sub F/ and thus resembled a noble metal as opposed to a transition metal. A test of this observation was provided by extensive studies of the chemical reactivity of CO on Pd overlayers supported on Ta, where it was found that both incommensurate and commensurate Pd monolayers behaved like a noble metal. Hence, it is suggested that the observation that CO does not chemisorb at room temperature on Pd monolayers does not depend on surface structure but instead is related to the electronic structure of the overlayer, namely the virtual absence of d-states near E/sub F/. Additional insights into the bonding between the substrate and the overlayer were provided by experiments where information could be obtained from core levels. The quality of the overlayer-substrate interface could be deduced from the nature of these levels and estimates of the bonding energies could be made from core level shifts.

• Research Organization: Rensselaer Polytechnic Inst., Troy, NY (USA)
• OSTI ID: 5792085
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
CHEMICAL REACTIONS
CHEMISORPTION
DEPOSITION
ELECTRONIC STRUCTURE
ELEMENTS
EMISSION
METALS
NICKEL
PALLADIUM
PHOTOEMISSION
PLATINUM
PLATINUM METALS
SECONDARY EMISSION
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SUBSTRATES
SURFACE PROPERTIES
TANTALUM
TRANSITION ELEMENTS