ZnSe light-emitting diodes
We report the successful fabrication of ZnSe p-n junction light-emitting diodes in which Li and Cl are used as p-type and n-type dopants, respectively.
Materials Literature
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Photochromism of H2 and H3 centres in synthetic type Ib diamonds
Photochromism has been studied for irradiated type Ib diamonds which are then annealed above 1500 degrees C. This mainly involves H2 and H3 centres. When the samples are illuminated with light of wavelength shorter than 600 nm, absorption of H2 centres is reduced while that of H3 centres is enhanced. In the dark the p…
Hyperfine fields and electronic structures of the Heusler alloys Co2MnX (X=Al, Ga, Si, Ge, Sn)
Hyperfine fields and electronic structures were calculated by the KKR method to investigate the effects of the X atom on the magnetic properties of Co 2 MnX. The obtained magnetic moments of Co or Mn sites in Co 2 MnX are in good agreement with the experimental ones. Though the obtained hyperfine fields on Co or Mn si…
Magnetism in ludlamite, Fe3(PO4)2.4H2O
The magnetic structure of the weak ferromagnet ludlamite, Fe3(PO4)2.4H2O, has been re-examined by both polarized and unpolarized neutron diffraction from single crystal samples of the mineral. The crystal structure has been refined from three dimensional data collected at 20 K, the unit cell being monoclinic, a=10.542…
Lattice dynamics and structural phase transitions in the chain compounds TMMC and TMCC. I. Structural study
The structural phase transitions occurring in the chain compounds (CH 3 ) 4 NMnCl 3 (TMMC) and (CH 3 ) 4 NCdCl 3 (TMCC) are studied through X-ray diffraction measurements. In both compounds, the existence of a new high-temperature orientationally disordered phase is established (phase I') with space group P6 3 /mmc an…
Nonlinear conductivity of quasi-one-dimensional TaS 3 at low temperatures
The nonlinear conductivity in orthorhombic and monoclinic TaS 3 has been measured as a function of temperature from the Peierls transition temperature down to 4.2 K in the electric field range 10 -2 -500 V cm -1 . At liquid-helium temperature a sharp increase in conductivity is measured in a very limited variation ran…
X-ray determination of the molecular tilt and layer fluctuation profiles of freely suspended liquid-crystal films
X-ray diffraction has been used to study the interlayer structure of fluid freely suspended liquid-crystal films versus film thickness. The observed scattering is described extremely well by a simple interlayer density model based on predicted layer fluctuation ${\mathrm{\ensuremath{\sigma}}}_{\mathit{i}}$ and tilt an…
Elastic constants of the hard-sphere glass: a density functional approach
The free energy and the static elastic constants of a hard-sphere glass are calculated using density functional theory. More specifically, Bennett's glass model is used where the packing fraction of random closed packing, eta RCP , is taken as an adjustable parameter. As regards the density functional, the modified we…
Non-resonant energy transfer between Tb3+and Eu3+in the cubic hexachloroelpasolite crystals Cs2NaTb1-xEuxCl6(x=0.01-0.15)
Luminescence decay curves have been measured for the Eu 3+ emission and Tb 3+ emission in the cubic crystals Cs 2 NaTb 1-x Eu x Cl 6 at 80 and 293 K using pulsed dye laser excitation into the 5 D 4 state of Tb 3+ and the 5 D 1 state of Eu 3+ . For excitation of Tb 3+ , efficient energy transfer occurs to the 5 D 0 sta…
The scaling functions for the β-relaxation process of supercooled liquids and glasses
The scaling equations which determine the master functions for the beta -relaxation process within the mode coupling theory of supercooled liquids are reformulated such that a direct numerical solution becomes possible. Tables are presented that allow an accurate derivation of the scaling function and susceptibilities…
Saturation of the hyperpolarizability of oligothiophenes
We report the observation of saturation with chain length of the second hyperpolarizability of a series of long, well-defined, conjugated oligothiophenes. This saturation occurs at the same length as that of the band gap and of the polarizability, and is attributed to a saturation of the effective conjugation length.…
Anomalous diffusion in ‘‘living polymers’’: A genuine Levy flight?
We have observed anomalously enhanced self- (tracer) diffusion in systems of polymerlike breakable micelles. We argue that it provides the first experimental realization of a random walk for which the second moment of the jump-size distribution fails to exist (``Levy flight''). The basic mechanism is the following: Du…
Thermal conductivity, heat capacity and phase diagram of cyclooctanol in liquid, solid and glassy crystal states under high pressure
Using the transient hot-wire method, thermal conductivity and heat capacity per unit volume are measured for solid and liquid phases and glassy crystal states of cyclooctanol, and information is provided on the phase diagram under high pressure. A new solid phase (III) is detected and characterized as a normal crystal…
Electrical Activity of Impurities in β-Rhombohedral Boron
The data are obtained of the electrical activity of Fe, Ni, Mn, Cu, Te, Re, W in β-boron. These dopants are shown to be donors or acceptors depending on their disposition in nonequivalent voids of the lattice. Some information on the conduction mechanism and on the density of localized states in doped β-boron is also…
Aging, Annealing, and Dielectric Properties of Neodymium Oxide Thin Films
Thin film capacitors of AlNd2O3Al structure are fabricated by the resistive heating method under a vacuum of 2.66 × 10−3 Pa. The thicknesses of the dielectric films are measured by a multiple beam interferometer. Aging, annealing, and dielectric properties are studied in the frequency range 1 to 30 kHz at various te…
Plasmons in a superlattice with periodic defects
The plasmon excitation spectrum for a multiple-quantum-well superlattice with rectangular defect barriers in each quantum well is calculated in the random-phase approximation. It is demonstrated that both the intersubband and the intrasubband plasma frequencies can be effectively tuned subject to variations of the par…
Phonon-drag thermoelectric power inAlxGa1−xAs/GaAs heterojunctions at low temperatures
The phonon-drag thermoelectric power ${\mathit{S}}_{\mathit{g}}$ in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs heterojunctions at low temperatures (\ensuremath{\lesssim}5 K) is theoretically investigated based on the Cantrell-Butcher theory. The experimental data are well e…
The structures of alkalides and electrides. V. Structures of caesium bis(15-crown-5) kalide and rubidium bis(15-crown-5) rubidide
Cs + 2(C 10 H 20 O 5 )•K − (I) cristallise dans C2/m avec a=11,537, b=13,679, c=10,624 A, β=90,12 o , Z=2, affinement jusqu'a R=0,067. Rb + 2(C 10 H 20 O 5 ); Rb − cristallise dans C2/m avec a=11,635, b=13,855, c=10,556 A, β=88,82 o , Z=2, affinement jusqu'a R=0,053. Les deux composes sont isostructuraux avec Rb + (15…
X-ray photoelectron spectroscopic studies of conductive polypyrrole complexes chemically synthesized withFeCl3
Highly conductive polypyrrole complexes obtained from chemical polymerization and oxidation of pyrrole by ${\mathrm{FeCl}}_{3}$ were studied by x-ray photoelectron spectroscopy. Properly deconvoluted Cl 2p core-level spectra of the complexes suggest that the chlorine dopant can exist in three chemical states. Thus rea…
Helical Smectic A
A new liquid-crystalline phase has been discovered in a broad temperature region between the cholesteric and smectic-A phases for the mixture of cholesterylnonanoate and nonyloxybenzoic acid. This phase is a helical smectic A with local smectic ordering, helical macrostructure, significant rigidity in shear deformatio…