S. A. Shivashankar

Kinetics of hydrogen evolution on submicron size Co, Ni, Pd and Co–Ni alloy powder electrodes by d.c. polarization and a.c. impedance studies

Submicron size Co, Ni and Co–Ni alloy powders have been synthesized by the polyol method using the corresponding metal malonates and Pd powder by reduction of PdOx in methanol. The kinetics of the hydrogen evolution reaction (HER) in 6 M KOH electrolyte have been studied on electrodes made from the pressed powders. The d.c. polarization measurements have resulted in a value close to 120 mV decade−1 for the Tafel slope, suggesting that the HER follows the Volmer–Heyrovsky mechanism. The values of exchange current density (io) are in the range 1–10 mA cm−2 for electrodes fabricated in the study. The a.c. impedance spectra measured at several potentials in the HER region showed a single semicircle in the Nyquist plots. Exchange current density (io) and energy transfer coefficient (α) have been calculated by employing a nonlinear least square-fitting program.

Thin films of iron oxide by low pressure MOCVD using a novel precursor: tris(t-butyl-3-oxo-butanoato)iron(III)

Deposition of thin films of iron oxide on glass has been carried out using a novel precursor, tris(t-butyl-3-oxo-butanoato)iron(III), in a low-pressure metalorganic chemical vapor deposition (MOCVD) system. The new precursor was characterized for its thermal properties by thermogravimetry and differential thermal analysis. The films were characterized by X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscopy, and by optical measurements. XRD studies reveal that films grown at substrate temperatures below ~550 °C and at low oxygen flow rates comprise only the phase

High contrast imaging and thickness determination of graphene with in-column secondary electron microscopy

Fe_3O_4

Low-pressure MOCVD of Al2O3 films using aluminium acetylacetonate as precursor: nucleation and growth

(magnetite). At higher temperatures and at higher oxygen flow rates, an increasing proportion of

Thermogravimetric evaluation of the suitability of precursors for MOCVD

alpha-Fe_2O_3

Determination of interlayer composition at buried interfaces using soft x-ray resonant reflectivity

is formed along with

Metal–organic chemical vapour deposition of thin films of cobalt on different substrates: study of microstructure

Fe_3O_4

A novel Cu(II) chemical vapor deposition precursor: Synthesis, characterization, and chemical vapor deposition

. Films of magnetite grown under different reactive ambients—oxygen and nitrous oxide—have very different morphologies, as revealed by scanning electron microscopic studies.

Metalorganic chemical vapor deposition of highly oriented thin film composites of V2O5 and V6O13: Suppression of the metal–semiconductor transition in V6O13

We report a new method for quantitative estimation of graphene layer thicknesses using high contrast imaging of graphene films on insulating substrates with a scanning electron microscope. By detecting the attenuation of secondary electrons emitted from the substrate with an in-column low-energy electron detector, we have achieved very high thickness-dependent contrast that allows quantitative estimation of thickness up to several graphene layers. The nanometer scale spatial resolution of the electron micrographs also allows a simple structural characterization scheme for graphene, which has been applied to identify faults, wrinkles, voids, and patches of multilayer growth in large-area chemical vapor deposited graphene. We have discussed the factors, such as differential surface charging and electron beam induced current, that affect the contrast of graphene images in detail.

Synthesis of LiCo1-xNixO2 from a low temperature solution combustion route and characterization

A study of the deposition of aluminium oxide films by low-pressure metalorganic chemical vapour deposition from the complex aluminium acetylacetonate, in the absence of an oxidant gas, has been carried out. Depositions on to Si(100), stainless steel, and TiN-coated cemented carbide are found to be smooth, shiny, and blackish. SIMS, XPS and TEM analyses reveal that films deposited at temperatures as low as 600 degreesC contain small crystallites Of kappa-Al2O3, embedded in an amorphous matrix rich in graphitic carbon. Optical and scanning electron microscopy reveal a surface morphology made up of spherulites that suggests that film growth might involve a melting process. A nucleation and growth mechanism, involving the congruent melting clusters of precursor molecules on the hot substrate surface, is therefore invoked to explain these observations. An effort has been made experimentally to verify this proposed mechanism