• Fouran Singh

      Articles written in Bulletin of Materials Science

    • Thermally stimulated luminescence studies in combustion synthesized polycrystalline aluminum oxide

      K R Nagabhushana B N Lakshminarasappa D Revannasiddaiah Fouran Singh

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      Synthesis of materials by combustion technique results in homogeneous and fine crystalline product. Further, the technique became more popular since it not only saved time and energy but also was easy to process. Aluminum oxide phosphor was synthesized by using urea as fuel in combustion reaction. Photoluminescence (PL) and thermally stimulated luminescence (TSL) characteristics of 𝛾-irradiated aluminum oxide samples were studied. A broad PL emission with a peak at ∼ 465 nm and a pair of strong and sharp emissions with peaks at 679 and 695 nm were observed in 𝛾-rayed samples. The PL intensity was observed to increase with increase in 𝛾-ray dose. Two prominent and well resolved TSL glows with peaks at 210°C and 365°C were observed in all 𝛾-irradiated Al2O3 samples. The TSL intensity was also found to increase with increase in 𝛾-ray dose. The TSL glow curves indicated second order kinetics.

    • Photoluminescence and Raman studies in swift heavy ion irradiated polycrystalline aluminum oxide

      K R Nagabhushana B N Lakshminarasappa Fouran Singh

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      Polycrystalline aluminum oxide is synthesized by combustion technique and XRD studies of the sample revealed the 𝛼-phase. The synthesized sample is irradiated with 120 MeV swift Au9+ ions for the fluence in the range from 1 × 1011 to 1 × 1013 ions cm-2. A broad photoluminescence (PL) emission with peak at ∼447 nm and two sharp emissions with peak at ∼ 679 and ∼ 695 nm are observed in pristine when sample was excited with 326 nm. However, in the irradiated samples the PL intensity at ∼ 447, 679 and 695 nm decreases with increase in ion fluence. The 𝛼-Al2O3 gives rise to seven Raman modes with Raman intensity with peaks at ∼ 253, 396, 417, 546, 630, 842, 867 cm-1 observed in pristine. The intensity of these modes decreases with increase in ion fluence. However, the Raman modes observed at lower fluences are found to disappear at higher fluence.

    • Effect of Cu ion implantation on the structural and electrical properties of BiSbTe$_3$ single crystals


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      Invoking defects with ion implantation is an attractive means to modify the physical parameters of materials. In the present work, Cu ions at fluence (1 ${\times}$ 10$^{15}$ ions cm$^{-2}$) with 100 keV energy were implanted on BiSbTe$_3$ (BST) single crystals. The X-ray diffraction (XRD) measurements on pristine and Cu ion-implanted crystals demonstrate a decrease in lattice parameter (a = b) from 4.31 to 4.26 A$^º$ with an increment in ‘c’ lattice parameter from 30.47 to 30.48 A$^º$ with implantation. The peaks in XRD are shifted to lower 2${\theta}$, which are attributed to tensile strain induced in sample due to implantation. The composition of pristine BST crystal depicted from X-ray photoelectron spectroscopy is Bi:Sb:Te = 1.08:1.45:2.4. The implantation of Cu in BST single crystals is confirmed by energy dispersive X-ray technique. The resistivity measurements reveal a decrease in resistivity with implantation due to decrease in strain with Cu ion implantation. The Hall coefficient is found to be positive for both the samples signifying that the holes are the dominating charge carriers. A slight shift in Fermi level was observed with implantation. The magnetoresistance data is fitted with an equation $R(B)$ = c+b${\times}$B$^a$ using Python. The parameter c varies from ${\sim}$228 to ${\sim}$388.5 m${\Omega}$ for the pristine sample, whereas for implanted sample it varies from 5.89 to 6.66 m${\Omega}$ throughout the temperature range ${\sim}$4–300 K. This drastic reduction in c is due to the Cu ion implantation, which augments the metallic nature of the sample.

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      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
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      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
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