Hemantkumar N. Aiyer

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

Electron transport properties of carbon nanotubes

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A study of copper films obtained from the nebulized spray pyrolysis of different precursors

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

Tunneling studies on single crystals of superconducting Bi2Ca1−xYxSr2Cu2O8+δ

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Scanning tunneling microscopy and spectroscopy of C70 thin films

with an increase in the cluster size.

Fullerenes and other carbon forms: studies by STM and cognate techniques

Electrical resistivity measurements of bulk samples of carbon nanotubes show that the resistivity behaviour of nanotubes is comparable to that of graphite. Thermopower behaviour of nanotubes is similar to that of certain pyrolytic graphites. Tunneling conductance measurements on isolated tubes however show the existence of a conductance gap which increases with the inverse diameter of the tube.

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

Metallic copper films have been deposited on Si(100) substrates by nebulized spray pyrolysis of Cu(acac), Cu(hfac) and Cu(dpm). The structure and morphology of the films have been examined by x-ray diffraction and scanning electron microscopy. The films are polycrystalline in nature with a preferred (111) orientation. Based on the electrical resistivity data, various transport parameters of the films have been estimated. Growth kinetics and the environmental stability of the films from the precursors have been compared. Taking all the factors into account, Cu(dpm) seems to yield the best films of copper metal.

An investigation of well-characterized small gold clusters by photoelectron spectroscopy, tunneling spectroscopy, and cognate techniques

Abstract Tunneling studies have been carried out on single crystals of Bi 2 Ca 1− x Sr x Cu 2 O 8+δ over a wide range of compositions wherein the hole concentration varies by a factor of 2.5. The 2Δ value varies between 25 meV and 75 meV over the composition range studied, but scales with 2 Δ / k B T c ≈9.5 throughout.

Investigations of carbon nanotubes

Scanning tunneling microscopy of C70 films deposited on HOPG and gold substrates has been carried out to investigate the 2D packing, defects and disorder. Besides providing direct evidence for orientational disorder, high resolution images showing the carbon skeleton as well as the molecular arrangement in a solid solution of C70 and C60 are presented. Tunneling conductance measurements indicate a small gap in the C70 film deposited on HOPG substrate.

Oriented films of LaNiO3 and other members of the Lan+1NinO3n+1 series, LaCuO3−δ and Pb(Zr0.52Ti0.48)O3, obtained by nebulized spray pyrolysis

Solid-state properties of fullerenes C 60 and C 70 with particular reference to orientational ordering, structural features and photopolymerization of the films, ferromagnetism in C 60 -TDAE and interaction of fullerene surfaces with metal clusters are discussed. Electronic properties of nanotubes as well as features of metal-filled hyperfullerenes are presented. The need to study other interesting forms of carbon such as diamond-graphite hybrids is indicated.