Materials Literature
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The electronic structure of poly-3-hexylthiophene (P3HT) is studied in the solid state with photoelectron spectroscopy, as the polymer is gradually doped from NOPF6. Solubility and processability of P3HT allow for the preparation of very clean and very thin films, which are then doped without air-exposure. The evoluti…
In order to investigate the influence of chain length on the diffusion of small molecules in polymers, molecular dynamics simulations have been carried out for two model systems. One is the short chain model which is composed of 30 n-alkane-like chains each having 20 segments. The other is the infinite length chain mo…
Epitaxial growth of compound semiconductors on the (001) exhibits an asymmetry in the dislocation morphology in the two 〈110〉 directions for thicknesses near the critical thickness. The source of the asymmetry has been investigated by growth of a thickness wedge of p- and n-type GaAs0.95 P0.05 on GaAs by metalorganic…
A very high-resistivity value (ρ 4K ∼ 4300 μΩcm), associated to a strong negative temperature dependence (α = 1/ρ · Δρ/Δ T ∼ −10 −3 K −1 ), is measured in pure icosahedral Al 63 Cu 25 Fe 12 phases (a single grain and polyquasicrystalline samples). Moreover the resistivity of the defective as-quenched Al 63 Cu 25 Fe 12…
Cristallisation dans C2/c avec a=9,940, b=8,5483, c=28,762 A, β=93,683 o , Z=4; affinement jusqu'a R=0,033. La structure comprend un reseau a 3 dimensions d'octaedres FeO 6 ayant des coins en commun avec des groupements As 2 O 7 , et un espace interstitiel dans lequel sont situes les ions Na + . Ce squelette est decri…
We have observed evidence of an incommensurate structural distortion in the ternary chalcogenide ${\mathrm{Ta}}_{2}$${\mathrm{NiSe}}_{7}$. The structure of ${\mathrm{Ta}}_{2}$${\mathrm{NiSe}}_{7}$ is similar to ${\mathrm{FeNb}}_{3}$${\mathrm{Se}}_{10}$ with one tantalum-centered trigonal prismatic chain and two inequi…
A free-energy model for the inhomogeneous hard sphere fluid mixture was derived recently [Phys. Rev. Lett. 63, 980 (1989)] which is based on the fundamental geometric measures of the particles. It features convolution forms for the direct correlation functions as obtained by functional differentiation from the free en…
The zone-center magnon modes of LuFeO3 have been studied by first-order Raman scattering. At room temperature, the two magnon modes (M1 and M2) associated with the canted, antiferromagnetically ordered Fe3+ moments are seen at 18.5 and 22 cm−1, respectively. Their corresponding symmetries, determined through polarizat…
Nine SiO2 :GeO2 glasses were heated under an H2 or O2 atmosphere. In the H2 atmosphere optical absorption bands were induced at vacuum ultraviolet (VUV) (>6.22 eV), 5.14 eV (242 nm), 3.82 eV (325 nm), and 0.452 eV (2.75 μm). The intensities of all the induced bands are in linear relation with each other. Heat t…
A new procedure for generating networks of Si atoms with the properties of amorphous Si is presented. We have used ab initio molecular-dynamics simulations and a simple simulation procedure to produce cells with radial distribution functions, coordination defect concentrations, and vibrational densities of states in e…
In the Onsager theory for the phase transition from the isotropic fluid to the nematic liquid crystal phase, the Helmholtz free energy of a fluid of hard convex bodies (HCBs) is expressed as the sum of an entropy of a mixing-like term and an energy-like term (from the interaction of the HCBs). Whereas the Onsager theo…
Thin condensed layers of biphenyl have been studied by ultraviolet photoelectron spectroscopy (UPS) and electron-energy-loss spectroscopy (EELS) as a function of Cs doping in order to model the situation in a doped conducting polymer. The UPS spectra show the growth of gap states which are assigned to bipolaron format…
We have measured the transit times of longitudinal and shear ultrasonic waves in (AgI${)}_{\mathit{x}}$(${\mathrm{AgPO}}_{3}$${)}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ glasses, with 0\ensuremath{\le}x\ensuremath{\le}0.46, at temperatures between 80 and 360 K and at pressures up to 4 kbar at 196 K and/or 296 K. We have…
The optical constants of ${\mathrm{V}}_{2}$${\mathrm{O}}_{5}$ single crystals along the three principal crystallographic axes were measured with use of spectroscopic ellipsometry. Theoretical optical constants of ${\mathrm{V}}_{2}$${\mathrm{O}}_{5}$ were derived from band-structure calculations using the first-princip…
We study the short-time and long-time diffusion coefficients and the high-frequency and zero-frequency effective viscosity of a dilute suspension of sticky hard spheres with hydrodynamic interactions. Due to the singular nature of the hydrodynamic interactions near touching the transport coefficients are strongly affe…
In an attempt to understand angular-dependent oscillatory magnetoresistance phenomena recently discovered in organic conductors, calculations of magnetoresistance in quasi-two-dimensional systems were carried out in the framework of the Boltzmann transport theory. Calculated magnetoresistance curves show the angular-d…
Electron localization in the methyl-ring-substituted derivative of polyaniline (PAN), poly(o-toluidine) (POT), has been investigated by transport and magnetic measurements. The HCl salt of POT shows greater electron localization than that of PAN due to decreased interchain diffusion rate caused by increased interchain…
Barkhausen effect (BE) phenomenology in iron-based ferromagnetic alloys is investigated by a proper experimental method, in which BE experiments are restricted to the central part of the hysteresis loop, and the amplitude probability distribution, P0(Φ̇), and power spectrum, F(ω), of the B flux rate Φ̇ are measured un…
The Barkhausen effect (BE) in metallic ferromagnetic systems is theoretically investigated by a Langevin description of the stochastic motion of a domain wall in a randomly perturbed medium. BE statistical properties are calculated from approximate analytical solutions of the Fokker–Planck equation associated with the…
Measurements are reported for the dc as well as frequency-dependent (ac) conductivities (real and imaginary parts) for various compositions of the vanadium germanate glassy semiconductors in the temperature range 80--450 K. The experimental results are analyzed with reference to various theoretical models proposed for…