• A K Pal

      Articles written in Bulletin of Materials Science

    • Preparation and characterization of diamond films

      S Chaudhuri A K Pal

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      Diamond films were deposited by magnetron sputtering of vitreous carbon disc and also by plasma CVD technique using C2H2 + H2 or CO2 + H2 gas mixtures. The films were characterized by measuring the electrical, optical and microstructural properties. FTIR and Raman studies were carried out to study the effect ofsp2 andsp3 bonds present in the films. The films had a high mechanical stress which was determined from the broadening of the optical absorption tail in the films.

    • Grain-boundary scattering in semiconductor films

      A K Pal

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      Alternative technique for studying grain-boundary scattering phenomena in high-resistivity semiconducting films has been indicated. The combined effect of the presence of electric field and mechanical stress at the grain boundaries was considered. It is shown that the grain boundary potential, density of trap states, and carrier concentration of the films can be obtained by measuring reflectances of the films deposited on non-absorbing substrates.

    • Size quantization effects in optical and electrical properties of II–VI semiconductor films in nanocrystalline form

      A K Pal

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      The electrical properties of CdTe and optical properties of ZnS in nanocrystalline thin film form are studied with a view to have a clearer understanding of the optical processes and the carrier transport mechanisms in nanocrystalline II–VI semiconductors, in general. Nanocrystalline ZnS and CdTe films were deposited by magnetron sputtering of respective targets in argon plasma. The optical absorption data of nanocrystalline ZnS films (thickness 10–40 nm) could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites. The conductivity of CdTe (grain size within 4–4·7 nm) showed (T0/T)p dependence withp ∼ 0·5 indicating the presence of a Coulomb gap near the Fermi level. The width of the Coulomb gap varied within 0·02–0·04 eV depending on the deposition condition. The existing theoretical models were used for estimating hopping energy (0·02–0·04 eV) and hopping distance (2·8–5·1 nm) in nano CdTe films.

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      Posted on October 12, 2020

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      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
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