• S A Shivashankar

      Articles written in Bulletin of Materials Science

    • Thermodynamic analysis of the metal-insulator transitions in V2O3 alloy systems

      J M Honig H V Keer G M Joshi S A Shivashankar

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      An overview is presented concerning the entropies (ΔS) and enthalpies (ΔH) associated with metal-insulator transitions in the (V1−xMx)2O3 M=Al, Cr, Ti systems, 0⩽x⩽0·12 and in non-stoichiometric V2(1 −y)O3, 0⩽y⩽0·01. The recent literature and new data are analyzed with respect to gradiations in ΔH and ΔS withx ory, and their implications concerning the mechanism of the transitions. A revised phase diagram is presented.

    • Nucleation and growth study of copper thin films on different substrates and wetting layers by metal-organic chemical vapour deposition

      A Dutta J Goswami S A Shivashankar

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      Chemical vapour deposition of copper thin films on different diffusion barrier/adhesion promoter layers have been studied. Copper thin films were grown in low pressure CVD reactor, using Cu(dpm)2 as precursor and argon as carrier gas. Growth rates, film adhesion to the substrate, and surface morphology were studied in detail.

    • Monte Carlo simulation of nucleation and growth of thin films

      J Goswami G Ananthakrishna S A Shivashankar

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      We study thin film growth using a lattice-gas, solid-on-solid model employing the Monte Carlo technique. The model is applied to chemical vapour deposition (CVD) by including the rate of arrival of the precursor molecules and their dissociation. We include several types of migration energies including the edge migration energy which allows the diffusive movement of the monomer along the interface of the growing film, as well as a migration energy which allows for motion transverse to the interface. Several well-known features of thin film growth are mimicked by this model, including some features of thin copper films growth by CVD. Other features reproduced are—compact clusters, fractal-like clusters, Frank-van der Merwe layer-by-layer growth and Volmer-Weber island growth. This method is applicable to film growth both by CVD and by physical vapour deposition (PVD).

    • Microwave-assisted synthesis of reduced graphene oxide/V$_2$O$_5$ nano-composite as an efficient photocatalyst for dye degradation

      DEVANSHI BHARDWAJ SAHIL SANGWAN S A SHIVASHANKAR A M UMARJI

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      In the present study, rapid and green microwave synthesis has been used to synthesize V$_2$O$_5$ and reduced graphene oxide decorated with V$_2$O$_5$, a hybrid nanocomposite (rGO/V$_2$O$_5$), using an inorganic precursor. The synthesized nanocomposite is characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and UV–visible spectroscopy. The photocatalytic activity of V$_2$O$_5$and rGO/V$_2$O$_5$ was studied by degrading methylene blue dye in sunlight. The kinetics of the dye degradation is studied by calculating the rate constant and the half-life of the degradation process. The rGO/V$_2$O$_5$ nanocomposite showed low resistance, thus increasing the diffusion of electrons, which prevents electron–hole recombination and hence enhances photocatalytic activity (80% degradation efficiency) when compared with bare V$_2$O$_5$.

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      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

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