Materials Literature
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Abstract In diesem Übersichtartikel werden chemische Aspekte der Herstellung von Oxiden nach Sol‐Gel‐Methoden näher beschrieben. Der Molekülchemie bieten sich in diesem Forschungsbereich interessante Möglichkeiten, wovon einige hier vorgestellt werden: 1) Vorstufen mit funktionellen Gruppen zur gezielten Herstellung v…
We present calculated electron excitation spectra for the LaM${\mathrm{O}}_{3}$ series (M=Cr-Ni) obtained within ab initio band-structure calculations for the real geometric and magnetic structures. The calculated results show good agreement with the experimentally obtained spectra. This suggests that the transition-m…
We have studied optical properties of oriented crystalline oligothiophene films on fused silica glasses. In crystalline films, the lowest absorption band of isolated molecules is split into a weak lower-energy band and a strong higher-energy band. The absorption spectra depend on the polarization of oblique incident l…
Amorphous silicon powders prepared by plasma-enhanced chemical vapor deposition, of 8--24-nm-sized particles agglomerated into larger aggregates were annealed in a reducing atmosphere to study the phase transformation behavior of these particles. High-resolution electron microscopy revealed a very rough surface, with…
The dynamics of optically generated excitations in a poly-(para)-phenylene--type ladder polymer has been investigated by means of femtosecond pump-probe as well as femtosecond luminescence up-conversion spectroscopy. In addition to the bulk emission a low-energy emission band assigned to physical aggregates is observe…
The electron field emission properties of the (111)1×1:H surface of natural semiconducting (p-type) diamond have been examined with simultaneous field emission and photoemission measurements. We find that the origin of the field emission is due to the electron tunneling from the valence band and show that the shape of…
When a chemical reaction such as \(A \rightleftharpoons B\) takes place simultaneously with a macrophase separation, mesoscopic structures similar to the patterns emerging during microphase separation appear. Since in a chemical system we can easily control the concentrations of the two species and reaction rates and…
To date, optical diffraction gratings filled with liquid crystals have not produced high (>50%) diffraction efficiencies in nonzero diffractive orders. Rigorous coupled-wave analysis indicates, however, that very high diffraction efficiencies (99% in single-wavelength polarized illumination) are theoretically feasible…
Alumina samples with different magnesia concentrations between 0.02 and 1 wt% have been sintered and characterized by electron microscopy. Their dielectric properties between 1 kHz and 15 GHz are studied. Different dielectric behaviors are found for different magnesia concentrations. A model based mainly on dipolar re…
InAs(001)-c(8\ifmmode\times\else\texttimes\fi{}2), InSb(001)-c(8\ifmmode\times\else\texttimes\fi{}2), and several reconstructions of GaAs(001) are exposed at room temperature to iodine molecules (${\mathrm{I}}_{2}$). Low-energy electron diffraction (LEED) and synchrotron soft x-ray photoelectron spectroscopy (SXPS) ar…
The electronic structure and the optical properties of the icosahedral ${\mathrm{B}}_{12}$${\mathrm{O}}_{2}$ crystal are studied by means of first-principles calculations. The results are compared with the other ${\mathrm{B}}_{12}$-based compounds with the same rhombohedral crystal structure. ${\mathrm{B}}_{12}$${\mat…
The standard theoretical model of two-level systems in low-temperature glasses is modified so that the temperature dependence of the effective homogeneous optical linewidth is in agreement with experiment. This alters the time dependence of the width due to spectral diffusion. The new results fit recent experiments wi…
We studied the confinement effects on the phonon spectra of CdTe quantum dots by means of resonant Raman scattering measurements. The spectra show clearly longitudinal optical phonons, surface phonons and some of their overtone combinations. We show that the scattering due to surface phonons increases as the quantum d…
Measurements of the temperature dependent transport properties of epitaxial BaTiO3 are reported. Electrical resistivity and thermoelectric power were measured over the temperature range of 77–300 K. Room temperature resistivities of the as-deposited, undoped films range from 105 to 108 Ω cm, while values as low as 55…
We report the properties of an all-solid-state electrochromic (EC) device that can be switched over a useful range of optical transmissions with voltages below 1 V. This switching voltage is smaller than required by other solid-state EC devices reported to date. We attribute the lower-than-normal switching voltage to…
The hexagonal ZnS nanocrystals were synthesized in polymer matrix. The ZnS polymer composite doped with tetraphenylbenzidine (TPB) as light-emitting layer was used to fabricate a single layer structure light-emitting diode which has a low turn on voltage such as 2.5 V. The electroluminescence spectrum was obtained at…
Oriented thin-film tin-doped indium oxide (ITO) was heteroepitaxially grown on optically polished (100) or (111) planes of single-crystalline yttria-stabilized zirconia (YSZ) substrates using e-beam evaporation or dc magnetron sputtering techniques. Pole figure x-ray diffraction analyses revealed that the heteroepitax…
The intra-4f transition close to 1.54 \ensuremath{\mu}m of Er implanted into Si shows rich fine structure due to the crystal field of different defect types. Making use of the influence of implantation and annealing parameters, additional doping, temperature, and excitation power, we identify groups of lines belonging…
The response of aluminum oxide-filled poly(dimethyl siloxane) and poly(diphenylsiloxane-co-dimethylsiloxane) elastomers, containing 3–24 mol % diphenylsiloxane, to cyclic stress at elevated temperatures (dynamic creep) was evaluated. The materials could be divided into two classes, based on their response to the appli…
The excitons in near-surface ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}/\mathrm{GaAs}$ QW's have been investigated by photoluminescence excitation and magnetophotoluminescence spectroscopy. The dielectric enhancement of excitons is demonstrated by measuring the splitting of the $2s$ and $1s$ exciton…