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Title: The surface chemistry of niobium monoxide: Three low miller index crystal faces

Miscellaneous ·
OSTI ID:6410004

The stoichiometry, structure, and surface chemistry of the (100), (110), and (111) crystal facets of NbO have been investigated using ultrahigh-vacuum surface-science techniques. Single crystals of NbO were grown by the Czochralski technique for use in these experiments. Auger electron spectroscopy and X-ray photoelectron spectroscopy (XPS) have been used to determine the stoichiometry and chemical state of the three NbO surfaces. The structure of the three crystal faces was examined by low energy electron diffraction (LEED). Surface chemistry was probed by performing temperature programmed desorption (TPD) experiments with water, CO, alcohols, n-hexane, and ethene. The strength of the interactions of these molecules with the surfaces studied provide information on the types of chemistry taking place on the surface. The three, clean NbO surfaces showed a slight oxidation of the surface compared to bulk stoichiometry as determined by XPS. The LEED patterns of the three NbO crystal facets were consistent with surface structures expected from termination of the bulk NbO structure. The superlattice spots present in all the LEED patterns were consistent with the ordered vacancies in the bulk crystal structure. The surfaces could be oxidized, with high oxygen exposure, to a stoichiometry of NbO{sub 2.3}. We hypothesize NbO{sub 2} as the surface compound. The carbon peak shape of the Auger spectrum indicated formation of a carbide surface under certain surface conditions. The surface chemical studies indicated that the NbO surfaces interacted more strongly with alcohols than with water or CO. Hexane and ethene both bonded weakly to the surfaces as well. Interesting reforming or isomerization products were observed for a few adsorbate/surface systems. Some of these products have been tentatively identified.

Research Organization:
California Univ., Berkeley, CA (USA)
OSTI ID:
6410004
Resource Relation:
Other Information: Thesis (Ph. D.)
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
NIOBIUM OXIDES
CHEMICAL PROPERTIES
CRYSTAL STRUCTURE
SURFACE PROPERTIES
ALCOHOLS
AUGER ELECTRON SPECTROSCOPY
CARBON MONOXIDE
CATALYTIC REFORMING
CHEMICAL ANALYSIS
CRYSTAL GROWTH
DESORPTION
ELECTRON DIFFRACTION
ETHYLENE
HEXANE
ISOMERIZATION
NIOBIUM CARBIDES
OXIDATION
PHOTOELECTRON SPECTROSCOPY
STOICHIOMETRY
TEMPERATURE CONTROL
WATER
X-RAY SPECTROSCOPY
ALKANES
ALKENES
CARBIDES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CONTROL
DIFFRACTION
ELECTRON SPECTROSCOPY
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
NIOBIUM COMPOUNDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
REFORMER PROCESSES
REFRACTORY METAL COMPOUNDS
SCATTERING
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies