Photoelectron spectroscopy studies of mixed-valence states of Sm overlayers on transition-metal surfaces

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5702828

Tao, Lian

To investigate and understand how the mixed-valent state of rare earths (RE) is formed and affected by their interactions with transition metals (TM), synchrotron-radiation-excited photoelectron spectroscopy was used to systematically study valence states of Sm overlayers on three TM surfaces as functions of Sm coverages. On polycrystalline Ta, Sm always has a mixed-valent state, consisting of the trivalent state and the divalent state. At a coverage of 0.02 monolayer, Sm has an average valence of 2.24. As the coverage increases, the Sm{sup 3+} and Sm{sup 2+} components increase at different rates. Sm on polycrystalline Cu behaves quite differently. At coverages below one monolayer, all the Sm ions adopt the trivalent state. When the coverage exceeds one monolayer, Sm{sup 2+} ions appear, with a resulting average valence of 2.52. After that the average valence does not change significantly. On a Cu(110) single crystal surface, the situation is found to closely resemble that observed on polycrystalline Cu. These results indicate that the Sm-Ta interaction is weak compared to the Sm-Sm interaction, while the Sm-Cu interaction is stronger and affects the electronic structure.

• Research Organization: New York Univ., NY (United States)
• OSTI ID: 5702828
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
665100 -- Nuclear Techniques in Condensed Matter Physics -- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BREMSSTRAHLUNG
COPPER
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
ELECTRONIC STRUCTURE
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
LAYERS
LEPTONS
METALS
PHOTOELECTRON SPECTROSCOPY
RADIATIONS
RARE EARTHS
SAMARIUM
SPECTROSCOPY
SUBSTRATES
SYNCHROTRON RADIATION
TANTALUM
TRANSITION ELEMENTS
VALENCE