Cluster size effects on sintering, CO adsorption, and implantation in Ir/SiO{sub 2}

Journal Article · Mon Sep 21 00:00:00 EDT 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3224119· OSTI ID:21559777

Kaden, W E; Kunkel, W A; Anderson, Scott L ^[1]

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1. Department of Chemistry, University of Utah, 315 S. 1400 E. RM 2020, Salt Lake City, Utah 84112-0850 (United States)

A series of planar model catalysts have been prepared via deposition of Ir{sub n}{sup +} on thermally grown amorphous SiO{sub 2}/Si(100) and ion scattering spectroscopy was used to probe surface structure as a function of cluster size, impact energy, and surface temperature. Deposition of Ir{sub 2} or Ir{sub 10} at low energies and room temperature results in stable clusters forming one- or two-dimensional single layer islands on the oxide surface. Heating the samples to 750 K leads to agglomeration, forming multilayer structures on the surface. Ir{sub 1} deposited under similar conditions sinters into large clusters at room temperature. Deposition at 110 K at least partially stabilizes the Ir atoms with respect to diffusion and sintering. At higher deposition energies, partial implantation into the surface is observed, but this appears to be insufficient to stabilize the clusters against sintering at elevated temperature. At low temperatures, substrate-mediated adsorption of CO is found to be highly efficient, leading to near saturation coverages of CO bound atop the Ir{sub n} clusters. The CO can be removed by careful He{sup +} sputtering. The deposition/binding behavior of Ir{sub n} on SiO{sub 2} is quite different from Ir{sub n}/TiO{sub 2}(110), for which the clusters bind in three-dimensional morphology, starting at Ir{sub 5}. That system also shows substrate-mediated adsorption of CO, but the CO preferentially binds at the periphery of the clusters rather than on top.

• OSTI ID: 21559777
• Journal Information: Journal of Chemical Physics, Vol. 131, Issue 11; Other Information: DOI: 10.1063/1.3224119; (c) 2009 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ADSORPTION
AGGLOMERATION
CARBON MONOXIDE
CATALYSTS
DEPOSITION
DIFFUSION
HEAT TREATMENTS
HELIUM IONS
ION IMPLANTATION
LAYERS
SILICA
SILICON OXIDES
SINTERING
SINTERS
SUBSTRATES
SURFACES
TEMPERATURE RANGE 0065-0273 K
THIN FILMS
TITANIUM OXIDES
TWO-DIMENSIONAL CALCULATIONS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHARGED PARTICLES
FABRICATION
FILMS
IONS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
SILICON COMPOUNDS
SORPTION
TEMPERATURE RANGE
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS