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Singh A.K.,Indian Institute of Physics
AIP Advances

Composite can alter the individual element physical property, could be useful to define the specific use of the material. Therefore, work demonstrates the synthesis of a new composition Se96-Zn2-Sb2 and its composites with 0.05% multi-walled carbon nano tubes and 0.05% bilayer graphene, in the glassy form. The diffused amorphous structure of the multi walled carbon nano tubes and bilayer gaphene in the Se96-Zn 2-Sb2 alloy have been analyzed by using the Raman, X-ray photoluminescence spectroscopy, Furrier transmission infrared spectra, photoluminescence, UV/visible absorption spectroscopic measurements. The diffused prime Raman bands (G and D) have been appeared for the multi walled carbon nano tubes and graphene composites, while the X-ray photoluminescence core energy levels peak shifts have been observed for the composite materials. Subsequently the photoluminescence property at room temperature and a drastic enhancement (upto 80%) in infrared transmission percentage has been obtained for the bilayer graphene composite, along with optical energy band gaps for these materials have been evaluated 1.37, 1.39 and 1.41 eV. © 2013 Author(s). Source

Singh A.K.,Indian Institute of Physics
Journal of Advanced Microscopy Research

Microscopic analysis can be useful to describe a material at the nanoscale, specifically composite materials surface morphology can be visualized from the field emission scanning electron microscopy. Subsequently with the help of energy dispersive spectroscopy and corresponding elemental mapping the elemental concentration at the microscopic level distribution can be described. Therefore, work describes a brief introduction of the microscopy along with amorphous/amorphous embedded morphologies for the Se55Te 25Ge20 alloy Se55Te25Ge 20+ 0.025% multiwalled carbon nanotubes and Se55Te 25Ge20 +0.025% bilayer graphene composites. Outcomes demonstrates constituents of the Se55Te25Ge20 alloy could be inter into the carbon nanotubes side walls and between the bilayer graphitic sheets through the inclusion. Further the elemental presence and their alloying distribution have been discussed with the help of the energy dispersive spectroscopic spectrums analysis and elemental mapping. The multilayer carbon nanotubes composite has been exhibited a non homogenous alloying elemental distribution, in comparison to bilayer graphene composite. Copyright © 2012 American Scientific Publishers. Source

We study directional dependent band gap evolutions and metal-insulator transitions (MITs) in model quantum wire systems within the spin-orbit density wave (SODW) model. The evolution of MIT is studied as a function of varying anisotropy between the intra-wire hopping (t) and inter-wire hopping (t ) with Rashba spin-orbit coupling. We find that as long as the anisotropy ratio ( β =tt) remains below 0.5, and the Fermi surface nesting is tuned to (t) π = Q , 0 1 , an exotic SODW induced MIT easily develops, with its critical interaction strength increasing with increasing anisotropy. As π π 1 (2D system), the nesting vector switches to (t) π π = Q , 2 , making this state again suitable for an isotropic MIT. Finally, we discuss various physical consequences and possible applications of the directional dependent MIT. © 2016 IOP Publishing Ltd. Source

Singh A.K.,Indian Institute of Physics
Journal of Alloys and Compounds

Crystallization kinetics could be define the working limits of the material, thereby, this work is described the kinetics of Se96Zn 2Sb2 (SZS) chalcogenide alloy and its composites with 0.05% multi walled carbon nano tubes (MWCNT) and 0.05% graphene (GF). The crystallization kinetic parameters have been obtained using the Differential Scanning Calorimetric (DSC) measurement traces at 5, 10, 15 and 20 °C/min heating rates, by employing the different approximations at the glass transition, onset crystallization and peak crystallization temperatures. Subsequently, Hruby Hr glass forming ability parameter, thermal stability and nucleation and growth order parameter (n) and dimensional parameter (m) of the materials have also been discussed. Outcomes demonstrate these materials have a variation in kinetic parameters with the incorporation MWCNT and GF in SZS regime. It has been noticed MWCNT composite glass transition activation energy (Eg), onset crystallization temperature (Ec), peak crystallization (Ep) higher than GF composite while lowest for the parent alloy, however, a variation in Hr and thermal stability have been obtained for the composites. The overall two-one dimensional nucleation and growth mechanism have been evaluated for these materials. © 2012 Elsevier B.V. All rights reserved. Source

Chowdhury A.,Indian Institute of Physics | Bhattacharjee S.,Indian Institute of Physics
Journal of Physics D: Applied Physics

We present a systematic experimental investigation of low-energy (0-1 kV) ion irradiation induced changes in sheet resistivity and Debye temperatures in metallic nano-films of Ag, Cu and Al of thickness d/λo ∼ 2-5, where d is the film thickness and λo is the bulk mean free path, as a function of ion beam induced defects and impurities in a controlled manner. Ions of both atomic (Ne, Ar and Kr) and molecular (H 2, N2) gases are employed in the investigation and the number of defects and impurities in the nano-film can be varied in a controlled manner by varying the ionic mass number (1-84) and beam fluence (8.7 × 1015-1.4 × 1016 ions cm-2). Low-temperature measurements are carried out for pristine and irradiated films to obtain the residual sheet resistance (RRS). An empirical formula relating the variation of RRS with beam fluence and ionic mass number is proposed for the first time. The change in RRS is due to the large diffusion of the impurities inside the nano-films as confirmed from energy dispersive x-ray spectroscopy. The Debye temperature (ΘD) is determined from Bloch-Grüneisen fitting of the temperature variation of sheet resistance data and it is found that ΘD decreases with increase in both fluence and ionic mass number arising primarily from the change in bulk modulus of the nano-film. © 2013 IOP Publishing Ltd. Source

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