An investigation of bimetallic clusters by a combined use of electron microscopy and photoelectron spectroscopy: additive effects of alloying and cluster size on core-level binding energies

Santra, AK and Subbanna, GN and Rao, CNR (1994) An investigation of bimetallic clusters by a combined use of electron microscopy and photoelectron spectroscopy: additive effects of alloying and cluster size on core-level binding energies. In: Surface Science, 317 (1-2). pp. 259-268.

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Abstract

Bimetallic clusters of Ni-Pd, Cu-Ni, Cu-Au and Au-Ni deposited on amorphized graphite have been in- vestigated by a combined use of photoelectron spectroscopy and electron microscopy. Metal core-level binding energies (Pd 3d, Au 4f and Ni/Cu 2p) of the bimetallic clusters deposited on amorphized graphite have been measured for different coverages or mean cluster sizes. When the cluster is large, the core-level binding energy the major metallic component in the bimetallic clusters $(e.g. \hspace{2mm} Cu\hspace{2mm} in\hspace{2mm} Cu_3Au \hspace{2mm} or \hspace{2mm} Cu_7Ni_3)$ is close to that of the bulk metal while that of the minor component $(e.g. \hspace{2mm} Au \hspace{2mm} in \hspace{2mm} Cu_3Au \hspace{2mm} or \hspace{2mm} Ni \hspace{2mm} in \hspace{2mm} Cu_7Ni_3)$ shows the effect of alloying. The effect of alloying is found in the core-level energies of both Ni and Pd in the large clusters of $Ni_3Pd_2$. With the decrease in cluster size or coverage, the core-level binding energies of both the metals increase, just as in the case of monometallic clusters. The present results show the occurrence of parallel shifts in the core-level binding energy of metals due to alloying and cluster size effects, both the effects manifesting themselves in the small clusters. It is noteworthy that the core-level binding energy shifts in bimetallic clusters are distinctly different from those in bimetallic overlayers. Although alloy formation does not occur in the Au-Ni system in the bulk, the $Au_3Ni$ and $Ni_3Au$ clusters show variations in binding energies similar to the alloy clusters. It appears that alloying in the Au-Ni system may indeed occur in the nanometric regime of clusters.

Item Type:	Journal Article
Publication:	Surface Science
Publisher:	Elsevier
Additional Information:	The copyright of this article belongs to Elsevier.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	04 Jul 2006
Last Modified:	19 Sep 2010 04:29
URI:	http://eprints.iisc.ac.in/id/eprint/7809

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