• A K Pal

      Articles written in Bulletin of Materials Science

    • Synthesis of B–Sb by rapid thermal annealing of B/Sb multilayer films

      S N Das A K Pal

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      Group III–V compound B–Sb films were synthesized from B/Sb/…/B multilayer films deposited by electron gun evaporation onto silicon substrate and subjecting the above multilayer to rapid thermal annealing at 773 K for 3 min. The films were characterized by XRD, TEM, XPS and optical studies. XPS studies indicated the ratio of B : Sb ∼1. XRD and electron diffraction patterns indicated the reflections from (100), (111), (102) and (112) planes of zinc blende BSb. Band gap evaluated from optical studies was ∼ 0.51 eV. Refractive index of the films varied between 1.65 and 2.18 with increasing energy of incident photon and plasma frequency (𝜔p) was estimated to be ∼ 2.378 × 10-14 s-1. The effective mass was computed to be ∼ 0.0845 m𝑒.

    • Surface plasmon effect in nanocrystalline copper/DLC composite films by electrodeposition technique

      S Hussain A K Pal

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      Composite films of nanocrystalline copper embedded in DLC matrix prepared by electrodeposition technique were studied for their optical properties. Particle size and metal volume fractions were tailored by varying the amount of copper containing salt in the electrolyte. Blue-shift of the surface plasmon resonance peak in the absorbance spectra of the films was observed with the reduction in size and volume fraction of metal particles. Mie theory was found to describe the experimental spectra quite well.

    • Electrical and optical properties of silicon-doped gallium nitride polycrystalline films

      S R Bhattacharyya A K Pal

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      Si-doped GaN films in polycrystalline form were deposited on quartz substrates at deposition temperatures ranging from 300–623 K using r.f. sputtering technique. Electrical, optical and microstructural properties were studied for these films. It was observed that films deposited at room temperature contained mainly hexagonal gallium nitride (ℎ-GaN) while films deposited at 623 K were predominantly cubic (𝑐-GaN) in nature. The films deposited at intermediate temperatures were found to contain both the hexagonal and cubic phases of GaN. Studies on the variation of conductivity with temperature indicated Mott’s hopping for films containing 𝑐-GaN while Efros and Shklovskii (E–S) hopping within the Coulomb gap was found to dominate the carrier transport mechanism in the films containing ℎ-GaN. A crossover from Mott’s hopping to E–S hopping in the `soft’ Coulomb gap was noticed with lowering of temperature for films containing mixed phases of GaN. The relative intensity of the PL peak at ∼ 2.73 eV to that for peak at ∼ 3.11 eV appearing due to transitions from deep donor to valence band or shallow acceptors decreased significantly at higher temperature. Variation of band gap showed a bowing behaviour with the amount of cubic phase present in the films.

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    • 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

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      Posted on July 25, 2019

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