• C N R Rao

      Articles written in Pramana – Journal of Physics

    • Soft chemical routes to semiconductor nanostructures

      Ujjal K Gautam Kripasindhu Sardar F L Deepak C N R Rao

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      Soft chemistry has emerged as an important means of generating nanocrystals, nanowires and other nanostructures of semiconducting materials. We describe the synthesis of CdS and other metal chalcogenide nanocrystals by a solvothermal route. We also describe the synthesis of nanocrystals of AlN, GaN and InN by the reaction of hexamethyldisilazane with the corresponding metal chloride or metal cupferronate under solvothermal conditions. Nanowires of Se and Te have been obtained by a self-seeding solution-based method. A single source precursor based on urea complexes of metal chlorides gives rise to metal nitride nanocrystals, nanowires and nanotubes. The liquidliquid interface provides an excellent medium for preparing single-crystalline films of metal chalcogenides.

    • A single molecule switch based on two Pd nanocrystals linked by a conjugated dithiol

      Ved Varun Agrawal Reji Thomas G U Kulkarni C N R Rao

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      Tunneling spectroscopy measurements have been carried out on a single molecule device formed by two Pd nanocrystals (dia. ∼5 nm) electronically coupled by a conducting molecule, dimercaptodiphenylacetylene. TheI-V data, obtained by positioning the tip over a nanocrystal electrode, exhibit negative differential resistance (NDR) on a background M-I-M characteristics. The NDR feature occurs at ∼0.67 V at 300 K and shifts to a higher bias of 1.93 V at 90 K. When the tip is held in the middle region of the device, a Coulomb blockade region is observed (±∼0.3 V)

    • Temperature-dependent infrared reflectivity studies of multiferroic TbMnO3: Evidence for spin-phonon coupling

      Pradeep Kumar Surajit Saha C R Serrao A K Sood C N R Rao

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      We have measured near normal incidence far-infrared (FIR) reflectivity spectra of a single crystal of TbMnO3 from 10 K to 300 K in the spectral range of 50 cm-1 –700 cm-1. Fifteen transverse optic (TO) and longitudinal optic (LO) modes are identified in the imaginary part of the dielectric function $\varepsilon_{2} (\omega)$ and energy loss function Im($−1/\varepsilon(\omega))$, respectively. Some of the observed phonon modes show anomalous softening below the magnetic transition temperature $T_{N}$ ($\sim 46$ K). We attribute this anomalous softening to the spin-phonon coupling caused by phonon modulation of the superexchange integral between the Mn3+ spins. The effective charge of oxygen ($Z_{O}$) calculated using the measured LO–TO splitting increases below $T_{N}$.

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