Sarit K. Ghosh

Graphene Supported Graphone/Graphane Bilayer Nanostructure Material for Spintronics

We report an investigation into the magnetic and electronic properties of partially hydrogenated vertically aligned few layers graphene (FLG) synthesized by microwave plasma enhanced chemical vapor deposition. The FLG samples are hydrogenated at different substrate temperatures to alter the degree of hydrogenation and their depth profile. The unique morphology of the structure gives rise to a unique geometry in which graphane/graphone is supported by graphene layers in the bulk, which is very different from other widely studied structures such as one-dimensional nanoribbons. Synchrotron based x-ray absorption fine structure spectroscopy measurements have been used to investigate the electronic structure and the underlying hydrogenation mechanism responsible for the magnetic properties. While ferromagnetic interactions seem to be predominant, the presence of antiferromagnetic interaction was also observed. Free spins available via the conversion of sp2 to sp3 hybridized structures, and the possibility of unpaired electrons from defects induced upon hydrogenation are thought to be likely mechanisms for the observed ferromagnetic orders.

Electron Field Emission of Silicon-Doped Diamond-Like Carbon Thin Films

In this work we demonstrate that the field emission characteristics of disordered Si-doped diamond-like carbon (DLC) thin films depend not only on properties of the conductive clustered sp2 phase and the insulating sp3 matrix (or sp2/sp3 ratio) but also on the presence of Si–Hn and C–Hn species in the film. The presence of such species reduces the hardness of the film and simultaneously enhances the field emission performance. A turn on electric field (ETOF) of 6.76 V/µm produced a field emission current density of ~0.2 mA/cm2, when an electric field of ~20 V/µm was applied. The Fowler–Nordheim (FN) tunneling model is appropriate to explain the field emission mechanism only within limited range of the current density. However, it is found that there is an apparent crossover between space charge limited current (SCLC) and the Frenkel effect due to impurities incorporated during the fabrication of Si-DLC films. This combined effect (SCLC + Frenkel) allows for the emission of electrons from the top of the reduced barriers due to the formation of comparatively soft DLC:Si films. The emission also occurs through tunneling from one conductive cluster (sp2 C=C) to another separated by an insulating matrix (sp3 C–C) after reducing the effective depth of a trap on application of high electric field.

Double-phase transition and giant positive magnetoresistance in the quasi-skutterudite Gd3Ir4Sn13

The magnetic, thermodynamic, and electrical/thermal transport properties of the caged-structure quasi-skutterudite Gd3Ir4Sn13 are re-investigated. The magnetization M(T), the specific heat Cp(T), and the resistivity ρ(T) reveal a double-phase transition—at TN1 ∼ 10 K and at TN2 ∼ 8.8 K—which was not observed in the previous report on this compound. The antiferromagnetic transition is also visible in the thermal transport data, thereby suggesting a close connection between the electronic and lattice degrees of freedom in this Sn-based quasi-skutterudite. The temperature dependence of ρ(T) is analyzed in terms of a power-law for resistivity pertinent to Fermi liquid picture. Giant, positive magnetoresistance (MR) ≈ 80% is observed in Gd3Ir4Sn13 at 2 K with the application of 9 T. The giant MR and the double magnetic transition can be attributed to the quasi-cages and layered antiferromagnetic structure of Gd3Ir4Sn13 vulnerable to structural distortions and/or dipolar or spin-reorientation effects. The giant...

Field-insensitive heavy fermion features and phase transition in the caged-structure quasi-skutterudite Sm3 Ru4 Ge13

The robust field-insensitive heavy fermion features in Sm

Synergistic effect of graphene oxide on the methanol oxidation for fuel cell application

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Multifunctional performance of nanocrystalline tin oxide

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Antiferromagnetic Kondo lattice to intermediate valence transition in Ce(Au1−xNix)2Si2 (0≤x≤1)

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Stannous sulfide nanoparticles for supercapacitor application

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Magnetic ordering and crystal field effects in quasi-caged structure compound PrFe2Al8

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The influencing role of oxophilicity and surface area of the catalyst for electrochemical methanol oxidation reaction: a case study

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