Materials Literature
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Ein neuer Rekord ist die Gleichgewichtskonstante Kc von 1019, die für die Komproportionierung des Dieisen(II,III)-Komplexes 1 in Acetonitril bestimmt wurde. In Wasser ist der Kc-Wert von 1 viel geringer (107.9), jedoch immer noch höher als der des Creutz-Taube-Ions. Intervalence-Charge-Transfer-Banden treten bei 2520…
A GaN-based metal–insulator–semiconductor (MIS) structure has been fabricated by using ferroelectric Pb(Zr0.53Ti0.47)O3 instead of conventional oxides as insulator gate. Because of the polarization field provided by ferroelectric and the high dielectric constant of ferroelectric insulator, the capacitance–voltage char…
Nanoscale field-effect transistor (FET) has been fabricated from single-walled carbon nanotubes (CNTs). At ∼5 K, the transistor shows pronounced field effect. Most interestingly, reproducible spikes are observed in the channel conductance as a function of the gate voltage. These conductance spikes are attributed to va…
Photostimulated luminescence at room temperature was observed in a fluorozirconate glass which was doped with 1% Eu2+ or 1% Ce3+ and 5% Br− ions. Small crystals of BaBr2 (high-pressure phase) form in the glass on cooling. The Eu2+ and Ce3+ luminescence spectra comprised two emission lines each: for Eu2+ one line at 41…
We observe current rectification in a molecular diode consisting of a semiconducting single-wall carbon nanotube and an impurity. One-half of the nanotube has no impurity, and it has a current-voltage $(I\ensuremath{-}V)$ characteristic of a typical semiconducting nanotube. The other half of the nanotube has the impur…
Many liquid crystal compounds are known to give structures periodic in only one direction, say z , with a period p comparable with the light wavelength . Their optical properties are fully defined by a dielectric tensor field ( z ), which for most crystals is well known. For p < , the periodic structures behave optica…
Local environment surrounding Y atoms in Y2O3:Tb nanocrystals under various heat treatment conditions has been investigated by using the extended x-ray absorption fine structure (EXAFS) technique. X-ray excited luminescence (XEL) with the incident x-ray energy near Y K edge and Tb L edges has also been measured to inv…
Theoretical electronic structure studies of the ground state geometries, binding energies, and magnetic coupling of ${\mathrm{Cr}}_{2}{\mathrm{O}}_{n}$ $(n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1--6)$ clusters have been carried out within a density functional scheme. It is shown that the magnetic coupling…
We observed violet/blue light emitted from cerium silicates which may be useful for silicon-based optoelectronics. The cerium silicate was produced during a rapid thermal annealing at high temperature (&gt;1100 °C) from the interface between silicon substrate and cerium oxide film. Detailed experiments including x…
Organic, nanoporous heterogeneous catalysts based on a carboxylate-containing, amphiphilic mesogen catalyze the Knoevenagel condensation (see schematic representation). These networks maintain their order in solution and can be recycled. Enhanced basicity, excellent site accessibility, and substrate size exclusion are…
By tailoring capillary interactions at a fluid-fluid interface, a hierarchical two-dimensional self-assembly of hexagonal millimeter-sized poly(dimethylsiloxane) plates has been demonstrated (see picture). The strength and direction of capillary forces between plates was controlled by patterning of the surfaces of the…
6.7 Gigatonnes of silicon are processed each year by marine organisms. Since it was known that silicon is an essential element for many biological systems, significant advances in the biochemistry of this element have been achieved from the classical viewpoint of silicon being a purely inorganic element. This article…
The concept of carrier pocket engineering is applied to strained Si/Ge superlattices to obtain a large thermoelectric figure of merit ZT. In this system, the effect of the lattice strain at the Si/Ge interfaces provides another degree of freedom to control the conduction band structure of the superlattice. We explore…
The observation of localized stationary structures, coined oscillons, in granular media has evoked much interest. By parametric excitation of clay suspensions, we demonstrate a hysteretic transition to oscillon-type states in a nongranular medium. When the symmetry of up-down $\mathrm{reflection}+\mathrm{time}$ transl…
We investigate the disordering of an initially phase-segregated binary alloy, due to a highly mobile defect which couples to an electric or gravitational field. Using both mean-field and Monte Carlo methods, we show that the late stages of this process exhibit dynamic scaling, characterized by a set of exponents and s…
We have shown that in narrow 2D semiconductor channels the D'yakonov-Perel' spin relaxation rate is strongly reduced. This relaxation slowdown appears in special waveguide diffusion modes which determine the propagation of spin density in long channels. Experiments are suggested to detect the theoretically predicted e…
We have used Raman spectroscopy to study indium nitride thin films grown by molecular beam epitaxy on (111) silicon substrates at temperatures between 450 and 550 C. The Raman spectra show well defined peaks at 443, 475, 491, and 591 cm{-1}, which correspond to the A_1(TO), E_1(TO), E_2^{high}, and A_1(LO) phonons of…
The atomic structure of icosahedral ${\mathrm{B}}_{4}\mathrm{C}$ boron carbide is determined by comparing existing infrared absorption and Raman diffusion measurements with the predictions of accurate ab initio lattice-dynamical calculations performed for different structural models, a task presently beyond x-ray and…
We present a quantitative description of the thermodynamics in a supercooled binary Lennard-Jones liquid via the evaluation of the degeneracy of the inherent structures, i.e., of the number of potential energy basins in configuration space. We find that the contribution of the inherent structures to the free energy of…
Poly(2-hydroxyethylmethacrylate) (PHEMA)-based microspheres (150–200 µm in diameter) were produced by a modified suspension polymerization of different type of comonomers—namely, acrylic acid, dimethylaminoethyl-methacrylate, and methylmethacrylate. These microspheres were activated with cyanogen bromide (CNBr) at pH…