Materials Literature
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In order to interpret the phonon-assisted optical transitions in semiconductor quantum dots, a theory is developed comprising the exciton interaction with both adiabatic and Jahn-Teller phonons and also the external nonadiabaticity (pseudo-Jahn-Teller effect). The effects of nonadiabaticity of the exciton-phonon syste…
High-resolution electron microscopy of amorphous interlayers (a-interlayer) formed by solid-state diffusion between metal thin films and silicon is reviewed. In this paper, an overview of the development is presented. Pertinent data obtained on the growth kinetics and structure of a-interlayers in polycrystalline meta…
Electronic structures of electron-doped ${\mathrm{SrTiO}}_{3\ensuremath{-}\ensuremath{\delta}}$ and ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{TiO}}_{3}$ have been investigated within the ab initio band-structure approach using a supercell containing eight basic units. A small amount of electron doping…
Hydrolysis of poly(L-lactide) (PLLA) films in 0.01N NaOH at 37°C was investigated by gel permeation chromatography, differential scanning calorimetry, scanning electron microscopy, and polarizing optical microscopy. The change in molecular weight distribution and surface morphology of PLLA films during hydrolysis reve…
The electronic structure of nitrogen-containing diamondlike films prepared by sputtering was determined by photoelectron spectroscopy. The $\mathrm{N}1s$ core-level spectra are constituted by two peaks at 400.5 and 398.2 eV associated with substitutional $\mathrm{N}{\mathrm{sp}}^{2}$ in aromatic rings and N bonded to…
The first and second hyperpolarizabilities (β and γ) of eight molecules at a fundamental wavelength of 1064 were measured by gas-phase electric-field-induced second-harmonic generation (EFISH), gas-phase hyper-Rayleigh scattering (HRS), and liquid-phase HRS experiments. The EFISH measurements give accurate values of β…
The electrical conductivity of a composite model system formed by highly structured carbon black (CB) filled, within an amorphous polymer, poly(ethylene terephtalate) composite is studied. The dc conductivity as a function of CB content follows a scaling law of the type $\ensuremath{\sigma}\ensuremath{\propto}(p\ensur…
A new class of self-assembling transmembrane ion channels based on cyclic β 3 -peptides is described. Cyclic peptide subunits were designed to adopt flat, ring shaped conformations and stack through extensive backbone-backbone hydrogen bonding to form tubular channel structures. Candidate channel-forming peptides cycl…
We point out a remarkable similarity between the resistivity behavior observed recently in single-wall carbon nanotubes and that of highly conducting polymers, in particular the change in sign of the resistivity temperature dependence from metallic to nonmetallic as the temperature is lowered. In analogy to the conduc…
We report experiments on gold clusters in the size range 2--4 nm, embedded in an alumina matrix. The metallic particles are produced with a laser vaporization source and codeposited with a dielectric vapor as a thin film on a substrate. Our technique allows varying the cluster size at a given metal concentration. Thes…
Thin films of fluorine-doped SnO2 have been prepared by deposition on borosilicate glass using the spray-pyrolysis technique. The effect of doping on the concentration and mobility of the charge carriers (electrons) as well as the resistivity of the films has been studied. The undoped films had a resistivity of a few…
Neutron-diffraction measurements have revealed a new anomalous thermal lattice expansion of LaCoO 3 near 500 K that indicates the existence of a second spin-state transition, in addition to the one previously established near 100 K. The anomalous expansion and the temperature dependence of the Co magnetic moments are…
A new technique of the simultaneous excitation of a magnetron sputtering discharge by rf and dc was used for the deposition of undoped ZnO- and Al-doped ZnO (ZnO:Al) films. By this technique, it was possible to change the ion-to-neutral ratio ji/jn on the substrates during the film growth by more than a factor of ten,…
Magnetotransport properties of $p$-type ferromagnetic (Ga,Mn)As, a diluted magnetic semiconductor based on III-V semiconductors, are measured and the $p\ensuremath{-}d$ exchange between holes and Mn $3d$ spins is determined. The ferromagnetic transition temperatures calculated based on the Ruderman-Kittel-Kasuya-Yosid…
We demonstrate how by taking better account of electron correlations in the $3d$ shell of metal ions in nickel oxide it is possible to improve the description of both electron energy loss spectra and parameters characterizing the structural stability of the material compared with local spin density functional theory.
ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionDoes Abalone Nacre Form by Heteroepitaxial Nucleation or by Growth through Mineral Bridges?Tilman E. Schäffer, Cristian Ionescu-Zanetti, Roger Proksch, Monika Fritz, Deron A. Walters, Nils Almqvist, Charlotte M. Zaremba, Angela M. Belcher, Bettye L. Smith, Galen D. S…
The whole conformation of a comb-like polymethacrylate (PMA-CH 3 ) has been determined by small-angle neutron scattering (SANS) in the isotropic and nematic phases. Its molecular weight dependence is obtained from six well-defined M values. In the isotropic phase, the persistence length is found to be l p = 10 ± 1.5 Å…
The deposition rate of calcium carbonate on a heat-transfer surface has been measured using a calcium-47 radiotracer and compared to the measured rate of thermal fouling. The crystalline phase of calcium carbonate that precipitates depends on the degree of supersaturation at the heat-transfer surface, with aragonite p…
The use of new “tailor-made” reactive statistical copolymers for the synthesis of sterically stabilized polypyrrole colloids is described. These copolymer stabilizers are readily prepared by free-radical copolymerization of (bi)thiophene-based vinylic monomers with various hydrophilic vinyl monomers such as 2-(dimethy…
Crystalline solids based on the tetrakis(4-cyanophenyl) and tetrakis(4-nitrophenyl) derivatives of zinc(II)-porphyrin or copper(II)-porphyrin as building blocks have been prepared and structurally analyzed by X-ray diffraction in order to elucidate the characteristic modes of self-assembly of these functionalized moie…