• S ANNAPOORNI

      Articles written in Bulletin of Materials Science

    • Preparation, characterization and optical properties ofα-Fe2O3 films by sol-spinning process

      Pratima Chauhan S Annapoorni S K Trikha

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      α-Fe2O3 films were prepared by sol-spinning process using ferric nitrate as a precursor and 2-methoxy ethanol as the solvent. The films were grown on various substrates by spin coating and were subjected to different annealing temperatures. These were characterized using X-ray and fourier transform infrared spectroscopy (FTIR). The films showed crystallinity at about 500°C. The surface morphology of these films was studied using scanning electron microscopy (SEM) which revealed cracks for films having thickness of the order of 2 µm. The band gap of these films was observed to be 2·1 eV from UV-vis spectroscopy.

    • Dense-plasma-driven ultrafast formation of FePt organization on silicon substrate

      ROHIT MEDWAL NEERU SEHDEV WANG YING R S RAWAT S ANNAPOORNI

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      This article demonstrates the removal of organic capping and promotion of long-range 2D organization of chemically synthesized FePt nanoparticles dispersed on Si$\langle 100\rangle$ substrate by means of pulsed H+ energetic ion irradiation using a dense plasma focus (DPF) device. The irradiation of energetic H$^+$ ions on FePt nanoparticles clearly resulted in enhanced structural and magnetic behaviour of the FePt nanoparticles as a function ofplasma focused irradiation shots. Transmission electron microscopy (TEM)/scanning electron microscopy (SEM) images of the FePt nanoparticles clearly show a marked enhancement in average particle size from 2.5 nm for nonirradiated sample to about 28nm for four plasma focus shots irradiation. The gradual removal of organic capping over chemically synthesized FePt nanoparticles with increasing plasma focus shots exposure is confirmed usingRaman spectroscopy. A uniform 2D organization of bimetallic FePt nanoparticles over 1 cm $\times$ 1 cm silicon substrate is obtained with three plasma focus shots with better magnetic properties as compared with plasma-untreated FePtnanoparticles.

    • A study on defect annealing in GaAs nanostructures by ion beam irradiation

      ONKAR MANGLA SAVITA ROY S ANNAPOORNI K ASOKAN

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      In this study, annealing of deep level (EL2) defect in gallium arsenide (GaAs) nanostructures by argon ion beam irradiation has been reported. GaAs nanodots of diameter ranging from 15 to 22 nm were deposited on silicon substratesusing the ions of GaAs generated by hot, dense and extremely non-equilibrium argon plasma in a modified dense plasma focus device. GaAs nanodots thus obtained were irradiated by Ar$^{2+}$ ion beam of energy 200 keV with varying ion fluences from $1 \times 10^{13}$ to $5 \times 10^{15}$ ions cm$^{−2}$ in the low energy ion-beam facility. The ion-beam irradiation transformed the as deposited GaAs nanodots into uniform GaAs nanostructured films of thickness $\sim$30 nm. The obtained nanostructured films are polycrystalline with paucity of arsenic antisite (EL2) deep level defect. The excess arsenic present in the as-deposited GaAs nanodots is the main cause of EL2 defect. Raman and photoluminescence measurements of GaAs nanostructured films indicates removal of excess arsenic, which was present in as-deposited GaAs nanodots, thereby suggesting annealing of EL2 defect from the ion-irradiated GaAs nanostructured films. The change in conductivity type from n- to p-type obtainedfrom Hall measurement further confirms annealing of EL2 defects. The ion-irradiated GaAs nanostructured films have low leakage current due to removal of defects as obtained in current–voltage study, which corroborate the annealing of EL2 defect. The defect-free GaAs nanostructured films thus obtained have potential applications in fabrication of highly efficient optoelectronic and electronic devices.

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      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

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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