• M S Hegde

      Articles written in Bulletin of Materials Science

    • Charge-transfer satellites in the x-ray photoelectron spectra of 3d° and 4d° metal oxides

      M S Hegde

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      O(2p)-metal (d) charge-transfer satellites in core level spectra of 3d° metal ions in CaO, Sc2O3, TiO2 and V2O5 and 4d° ions in SrO, Y2O3, ZrO2 and Nb2O5 have been reported. A systematic increase in the satellite separation is noticed going from CaO to V2O5 and from SrO to Nb2O5.

    • Low temperature preparation and characterization of intermetallics—Fe2W, FeMo and some ternary Fe-W-Mo systems

      T S Sampathkumar R M Mallya M S Hegde

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      Monophase Fe2W and FeMo intermetallics have been prepared by hydrogen reduction of Fe2WO6 and FeMoO4 oxides respectively below 1050 K. The ternary intermetallics Fe2W0·9Mo0·1 and FeMo0·9W0·1 have also been prepared by a similar method from the respective substituted oxides. The oxides and the intermetallics have been characterized by x-ray powder diffraction, x-ray photoelectron and Mössbauer spectroscopies. The observed negative isomer shift of Fe in the intermetallics is attributed to an increase in the electron density in Fe by electron transfer from W or Mo to Fe.

    • Growth and characterization of laser-deposited Ag-doped YBa2Cu3O7−x thin films on bare sapphire

      Dhananjay Kumar K M Satyalakshmi S S Manoharan M S Hegde

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      Microstructural and superconducting properties of YBa2Cu3O7−x thin films grownin situ on bare sapphire by pulsed laser deposition using YBa2Cu3O7−x targets doped with 7 and 10 wt% Ag have been studied. Ag-doped films grown at 730°C on sapphire have shown very significant improvement over the undoped YBa2Cu3O7−x films grown under identical condition. A zero resistance temperature of 90 K and a critical current density of 1·2×106 A/cm2 at 77 K have been achieved on bare sapphire for the first time. Improved connectivity among grains and reduced reaction rate between the substrate and the film caused due to Ag in the film are suggested to be responsible for this greatly improved transport properties.

    • Growth and applications of superconducting and nonsuperconducting oxide epitaxial films

      M S Hegde

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      Growth and characterization of high-temperature-superconducting YBa2Cu3O7 and several metallic-oxide thin films by pulsed laser deposition is described here. An overview of substrates employed for epitaxial growth of perovskite-related oxides is presented. Ag-doped YBa2Cu3O7 films grown on bare sapphire are shown to giveTc=90 K, critical current >106 A/cm2 at 77 K and surface resistance =450µΩ. Application of epitaxial metallic LaNiO3 thin films as an electrode for ferroelectric oxide and as a normal metal layer barrier in the superconductor-normal metal-superconductor (SNS) Josephson junction is presented. Observation of giant magnetoresistance (GMR) in the metallic La0·6Pb0·4MnO3 thin films up to 50% is highlighted.

    • Pulsed laser deposition of indium antimonide

      R Venkataraghavan K M Satyalakshmi K S R K Rao A K Sreedhar M S Hegde H L Bhat

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      Single crystalline oriented films of indium antimonide have been grown on cadmium telluride substrates by the pulsed laser deposition technique. The films were (111) oriented which is the substrate orientation. The composition of the grown films were found to deviate from that of the target owing to loss of antimony during evaporation. This deviation from stoichiometry led to film-substrate reaction, resulting in mixed interface. The antimony deficiency in the films were controlled by correcting the stoichiometry, which led to avoiding mixed interfaces. The stoichiometric films showed good surface morphology and well defined sharp interfaces. The IR transmission spectrum showed sharp band to band absorption and effective detection in the MWIR.

    • Synthesis, structure and IR absorption studies of LnBaCuCoO5 (Ln=rare earth) oxides

      C Shivakumara M S Hegde G N Subbanna

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      A series of oxides LnBaCuCoO5 (Ln=Pr, Nd, Sm, Dy, Gd, Ho and Er) have been synthesized by ceramic method. The oxides crystallize in a tetragonal structure, isostructural to YBaCuCoO5. All the oxides in the series are semiconducting. IR spectra of these oxides show distinct absorption bands at 630 cm−1, 550 cm−1 and 330 cm−1 which are assigned toE,A2 andA1 modes respectively. Doping of holes in these oxides, by calcium substitution in Er1−xCaxBaCuCoO5−x (up tox ⋍ 0·3) was done but, these oxides did not show metallic behaviour.

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