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Cluster size effects on sintering, CO adsorption, and implantation W. E. Kaden, W. A. Kunkel, and Scott L. Andersona
 

Summary: Cluster size effects on sintering, CO adsorption, and implantation
in Ir/SiO2
W. E. Kaden, W. A. Kunkel, and Scott L. Andersona
Department of Chemistry, University of Utah, 315 S. 1400 E. RM 2020, Salt Lake City,
Utah 84112-0850, USA
Received 8 May 2009; accepted 17 August 2009; published online 16 September 2009
A series of planar model catalysts have been prepared via deposition of Irn
+
on thermally grown
amorphous SiO2/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 Ir2 or Ir10 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. Ir1 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 Irn clusters. The CO can be
removed by careful He+

  

Source: Anderson, Scott L. - Department of Chemistry, University of Utah

 

Collections: Energy Storage, Conversion and Utilization; Materials Science; Chemistry