V. Vijayakrishnan

Investigations of Pd clusters by the combined use of HREM, STM, high-energy spectroscopies and tunneling conductance measurements

Palladium clusters deposited on carbon substrates by vacuum evaporation have been examined by high resolution electron microscopy and scanning tunneling microscopy to obtain the size distributions of the clusters. Pd(3d) binding energy of clusters of known size distributions have been measured to establish the variation of the binding energy with the cluster size. Clusters of a mean diameter of

A comparative study of the interaction of oxygen with clusters and single-crystal surfaces of nickel

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State of bismuth in BaBiO3 and BaBi1−xPbxO3: Bi 4f photoemission and Bi L3 absorption spectroscopic studies

1 nm which show the highest PdOd) binding energies relative to the bulk metal also show a conductance gap in tunneling spectroscopic measurements. The results show the occurrence of a size-dependent metal-to-nonmetal transition in Pd clusters. This conclusion is corroborated by valence band and bremsstrahlung isochromat spectroscopic measurements which show the emergence of new states closer to

Interaction of solid films of C60 and C70 with nickel

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A comparative study of the interaction of nickel clusters with buckminsterfullerene, C60, and graphite

with an increase in the cluster size.

Electronic structures and reactivities of monometallic and bimetallic clusters of Au and Cu

Abstract The interaction of oxygen with Ni(100), (110) and (111) surfaces as well as with Ni clusters of varying sizes has been investigated by employing core-level spectroscopy. On single-crystal surfaces, the main oxygen species are O 1− and O 2− with characteristic O(1s) binding energies of 531 and 530 eV, the percentage of the former being ∼30. At relatively high oxygen exposures, Ni 2+ and Ni 3+ are found on these surfaces. On the surfaces of small clusters, O 1− is the primary product (≥ 50%) and the proportion of the O 2− species increases with the cluster size. The small clusters distinctly show that Ni 2+ is formed first, followed by Ni 3+ at higher exposures. A sequence of transformations occurring on Ni surfaces exposed to oxygen is suggested.

A study of chemically prepared small metal clusters in the nonmetallic regime

The 2p 6d feature in the Bi L3 spectra has different energies in the semiconducting (0.0≤x<0.7) and the superconducting (x=0.75) compositions of BaBi1−xPbxO3. The Bi 4f core level spectrum shows distinct features ascribable to Bi III and Bi V in BaBiO3 and in the semiconducting compositions; the width of the 4f peaks is also considerably larger in these compositions compared to that in BaBi0.25Pb0.75O3, which shows a single sharp Bi 4f feature.

Investigations of the Interaction of Nickel and Carbon Monoxide with Solid Films of C60 and C70 by UV and X-Ray Photoelectron Spectroscopy

Abstract Interaction of varying coverages of Ni metal with solid films of C60 and C70 has been investigated by UV and X-ray photemission spectroscopy. The shifts in the valence bands of C60 (as well as of C70) with increasing Ni coverage accompanied by a shift of the C is level of the fullerene to lower binding energies suggest charge-transfer from the metal to the fullerene as in transition metal complexes of π-systems.

Interaction of nitrogen and oxygen with C60

Interaction of nickel deposited on multilayer films of C60 has been investigated in comparison with that on amorphized graphite by employing photoemission spectroscopy. It is shown that unlike with graphite, Ni interacts strongly with C60 causing large changes in C(1s) and C(2p) binding energies. The increase in the Ni(2p) binding energy at small Ni coverages is also far greater on c60 than on graphite.

Interaction of nitrogen with fullerenes: nitrogen derivatives of C60 and C70

The variation of the Au 4f binding energy of Au clusters with the cluster size has been established by measuring the binding energies of clusters whose size distributions were independently determined by HREM and STM. The binding energy increases significantly when the cluster size is less than ∼ 2 nm. Au-Cu bimetallic clusters of the composition Cu3Au have been deposited for the first time on carbon substrates. The shifts in the core level binding energies of the bimetallic clusters show the effect of alloying in the case of large clusters, but show effects of both alloying and cluster size in the case of the small clusters. The interaction of CO with Cu3Au clusters is stronger than with a bulk Cu metal. The interaction of CO with small Cu clusters also seems to be stronger than with bulk Cu or with large Cu clusters.