Showing papers by "Government College published in 1996"

Electronic conduction in Bi‐modified amorphous thin films of Ge20Te80‐x Bi x exhibiting an absence of a p‐n transition

Abstract: Ac conductivity and dielectric relaxation studies of well‐characterized Bi‐modified amorphous thin films of Ge20Te80‐x Bi x (x=0, 0.19, 2.93 and 7.35) prepared by flash evaporation, exhibiting an absence of p‐n transitions in the frequency range 500 Hz‐10 kHz and the temperature span 180 K‐450 K, are reported. The ac conductivity, σ ac(ω), is found to be proportional to ωs. The temperature dependences of σ ac(ω), and the exponent s are interpreted using the correlated‐barrier hopping model. It is revealed that electronic conduction takes place via bipolaron/single polaron hopping processes at low/high temperatures in all the compositions. At a lower Bi concentration (x=0.19), Bi‐induced defects that take part in single polaron hopping are produced. Further increases in the Bi concentration (x=2.93 and 7.35) cause little change in the density of such defects. The density of defect states taking part in bipolaron conduction is not significantly affected by addition of Bi atoms to the alloy. This fe...

Viscosity of nonelectrolyte liquid mixtures. IV. Binary mixtures containing p -Dioxane

Abstract: Measurements of the viscosityη and densityp are reported for eight binary mixtures ofp-dioxane with methylcyclohexane, l-chlorohexane, l-bromohexane, p-xylene, propylbenzene, methyl acetate, butyl acetate. anyl acetate at 303.15 K. The viscosity data haw been correlated with the equations of Grunbeng Nissan. of McAllister, and of Auslaendcr. The relation among the excess viscosityΔ Inη, excess Gibbs energy of activationΔG* E of viscous flow. and intermolecular interaction in these mixtures is discussed.

Surface morphology and optical properties of MeV-energy heavy-ion irradiated crystalline Si and crystalline Ge: Possibility of formation of porous material

Abstract: The effect of bombardment of crystalline Si (c-Si) and crystalline Ge (c-Ge) with 75MeV Ni+, Ge+ and Ag+ ions at room temperature and liquid-nitrogen temperature (LNT) at fluences in the range of 1 × 1013-1 × 1014 ions cm−2 has been investigated. The ion-induced damage brought about by electronic and nuclear energy losses on the surface and deep inside the bulk, has been monitored by scanning electron microscopy and optical spectroscopy. In an optical study, the effect has been studied by measuring the reflectivity R and transmittance T in the spectral range 200–2500 nm and by determining the optical constants, namely the absorption coefficient α and refractive index n. These studies indicate that the surface morphological changes depend strongly on the temperature of bombardment and the nature of the projectile ion. The most striking effect in both the crystals is seen with Ni + -ion bombardment at LNT, while no appreciable effect is observed with Ag+ ions. The possibility of the formation of el...

Peak shifts in magnetization rotation effects of anisotropy and pinning

Abstract: Magnetization rotation experiments have been performed on a melt-textured YBa 2 Cu 3 O 7− x sample in the field cooled and zero field cooled conditions. The data show significant shifts of the maxima and minima from their expected positions in M ( θ ), both in increasing angles as well as on the reversal of the sense of rotation. Our results have been explained using the concepts of the anisotropy of the flux line energy and the intrinsic torque within the framework of the generalized critical state model, which invokes the idea of a flux orientation gradient in addition to a gradient of flux density.

Effect of Sb on pressure induced transformation in Se-Te Glass

Abstract: High pressure dc conductivity measurements, in the pressure range 0 ≤ P ≤ 3 GPa, for Se80-xTe20Sbx (0 ≤ x ≤ 9) are reported. Glass transition temperature (Tg) and X-ray diffraction (XRD) studies have also been performed on the samples before and after the pressure cycle. Transformations, i.e. decrease of resistivity with pressure, are not only rapid and continuous but also reversible with hysteresis, which decreases as the Sb content increases. The transformation pressure (Ps) also shifts towards lower pressure with the increase of Sb content. An attempt has been made to understand the results in the light of bandgap model for amorphous chalcogenide glasses.