• S W Gosavi

      Articles written in Pramana – Journal of Physics

    • Synthesis and analysis of ZnO and CdSe nanoparticles

      Shriwas S Ashtaputre Aparna Deshpande Sonali Marathe M E Wankhede Jayashree Chimanpure Renu Pasricha J Urban S K Haram S W Gosavi S K Kulkarni

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      Zinc oxide and cadmium selenide particles in the nanometer size regime have been synthesized using chemical routes. The particles were capped using thioglycerol in case of ZnO and 2-mercaptoethanol in case of CdSe to achieve the stability and avoid the coalescence. Zinc oxide nanoparticles were doped with europium to study their optical properties. A variety of techniques like UV-Vis absorption spectroscopy, X-ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) were used to carry out structural and spectroscopic characterizations of the nanoparticles.

    • Synthesis and characterization of silica—titania core—shell particles

      Suchita Kalele Ravi Dey Neha Hebalkar J Urban S W Gosavi S K Kulkarni

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      Nearly monodispersed particles of silica were prepared and coated with uniform layers of titanium dioxide in anatase phase by hydrolysis and condensation of titanium butoxide. The coating thickness could be altered by adjusting the concentration of reactants (titanium butoxide and water) and the amount of added silica particles. Different coating thicknesses were deposited and studied using optical absorption spectroscopy, electron microscopy and Fourier transform infra-red spectroscopy. It was found that silica particles of size 170 ±5 nm were coated with 23±5 nm thick layer of titanium dioxide. Alternatively titania particles of size 340±5 nm were synthesized by controlled hydrolysis of titanium ethoxide in the presence of sodium chloride. These particles were further coated with 135±5 nm thick layer of silica to investigate changes in properties after changing the shell material

    • Determination of the optical parameters of a-Si:H thin films deposited by hot wire–chemical vapour deposition technique using transmission spectrum only

      Nabeel A Bakr A M Funde V S Waman M M Kamble R R Hawaldar D P Amalnerkar S W Gosavi S R Jadkar

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      Three demonstration samples of intrinsic hydrogenated amorphous silicon (a-Si:H) films were deposited using hot wire–chemical vapour deposition (HW–CVD) technique. The optical parameters and the thickness were determined from the extremes of the interference fringes of transmission spectrum in the range of 400–2500 nm using the envelope method. The calculated values of the refractive index (𝑛) were fitted using the two-term Cauchy dispersion relation and the static refractive index values ($n_0$) obtained were 2.799, 2.629 and 3.043 which were in the range of the reported values. The calculated thicknesses for all samples were cross-checked with Taly-Step profilometer and found to be almost equal. Detailed analysis was carried out to obtain the optical band gap ($E_g$) using Tauc’s method and the estimated values were 1.99, 2.01 and 1.75 eV. The optical band gap values were correlated with the hydrogen content ($C_H$) in the samples calculated from Fourier transform infrared (FTIR) analysis. An attempt was made to apply Wemple–DiDomenico single-effective oscillator model to the a-Si:H samples to calculate the optical parameters. The optical band gap obtained by Tauc’s method and the static refractive index calculated from Cauchy fitting are in good agreement with those obtained by the single-effective oscillator model. The real and the imaginary parts of dielectric constant ($\epsilon_r, \epsilon_i$), and the optical conductivity (𝜎) were also calculated.

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