Materials Literature
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We report on the growth of polarity-controlled ZnO films by plasma-assisted molecular-beam epitaxy. Different polar (Zn- and O-polar) ZnO films on unipolar (Ga-polar) GaN epilayers are selectively grown. Polarity of ZnO films is evaluated by coaxial impact collision ion scattering spectroscopy. Zn preexposure prior to…
We show that germanium dots can be directly grown by molecular beam epitaxy (MBE) on a silicon (001) surface covered by a thin (1.2-nm-thick) thermal silicon oxide layer. We describe the experimental procedure, which induces the growth of a high density (1011/cm2) of nanometric germanium dots on silicon oxide. Germani…
Longitudinal or transverse magnetic fields applied on a crystal of ${\mathrm{Mn}}_{12}$ acetate allows one to observe independent tunnel transitions between $m\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}S+p$ and $m\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}S\ensuremath{-}n\ensuremath{-}p$…
The crossover between thermally assisted and pure quantum tunneling has been studied in single crystals of high spin (S = 10) uniaxial molecular magnet Mn12 using micro-Hall-effect magnetometry. Magnetic hysteresis and relaxation experiments have been used to investigate the energy levels that determine the magnetizat…
The self-energy of the photohole in 2H-TaSe2 is measured by angle-resolved photoemission spectroscopy as a function of binding energy and temperature. In the charge-density wave (CDW) state, a structure in the self-energy is detected at approximately 65 meV that cannot be explained by electron-phonon scattering. A red…
Spin-dependent tunneling has been shown to occur through Ga2O3 as the insulating tunnel barrier. Magnetic tunnel junctions of the type Co/Ga2O3/Ni80Fe20 were prepared by oxidizing thin metal layer of Ga in oxygen plasma and characterized. The highest junction magnetoresistance observed was 18.2% at room temperature, i…
Ferroelectric intergrowth Bi4Ti3O12–SrBi4Ti4O15 has been demonstrated to have a large remanent polarization (2Pr) of 30 μC/cm2 and a high Curie temperature of 610 °C using bulk ceramics. The Rietveld analysis of the powder x-ray diffraction patterns showed that there are two kinds of Bi ions in Bi2O2 layers. One Bi io…
Carbon nanotube junctions are predicted to exhibit negative differential resistance, with very high peak-to-valley current ratios even at room temperature. We treat both nanotube p-n junctions and undoped metal-nanotube-metal junctions, calculating quantum transport through the self-consistent potential within a tight…
We study the response of an adsorbed monolayer under a driving force as a model of sliding friction phenomena between two crystalline surfaces with a boundary lubrication layer. Using Langevin-dynamics simulation, we determine the nonlinear response in the direction transverse to a high symmetry direction along which…
Effects of induced biaxial strain on the electrical transport and magnetic properties of epitaxial thin films of SrRuO3 and La0.67Sr0.33MnO3 by structural transitions of ferroelectric BaTiO3 substrates have been studied. Large jumps of electrical resistivity (∼5% in SrRuO3 and ∼12% in La0.67Sr0.33MnO3) and low field m…
We report an experimental system based on rigid, monodisperse, microparticles with tunable surface properties for the study of topological defects that form about dispersed solid phases in anisotropic media. We clearly observe equatorial Saturn-ring defects to form a distance (0.09+/-0.01)R from the surface of isolate…
The well-defined geometry and extreme structural anisotropy of a multiwalled carbon nanotube can bring qualitatively new features to its nanometer-scale tribology. Efficient cancellation of registration-dependent interactions in incommensurate tubes (and also, surprisingly, certain axial commensurate tubes) can induce…
A tricomponent system composed of resorcinol, hexamethylene tetramine (HMT), and hydrated silica was used as an adhesion promoter with a nitrile rubber (NBR) mix. The resorcinol was replaced by o-aminophenol, m-aminophenol, p-aminophenol, or m-phenylene diamine. The rubber–textile cord samples were subjected to aging…
A number of diverse bulk properties of the zincblende and wurtzite III-V nitrides AlN, GaN, and InN, are predicted from first principles within density functional theory using the plane-wave ultrasoft pseudopotential method, within both the LDA (local density) and GGA (generalized gradient) approximations to the excha…
The existing interpretation and models of electroluminescence (EL) in poly(ethylene-2, 6-naphthalate) (PEN) suggest a mechanism triggered by the impact excitation and/or ionization of the luminescent centres by hot electrons. Excitation by bipolar charge recombination has not been considered extensively because of the…
The enzyme magnesium protoporphyrin chelatase catalyses the insertion of magnesium into protoporphyrin, the first committed step in chlorophyll biosynthesis. Magnesium chelatase from the cyanobacterium Synechocystis PCC6803 has been reconstituted in a highly active state as a result of purifying the constituent protei…
Authors' address: Ludwig-Maximilians-Universitat Munchen, Zoological Institute, Department of Ecology, Karlstr. 25, D-80333 Munchen Germany.
Single-walled carbon nanotubes are ideal systems for investigating fundamental properties and applications of one-dimensional electronic systems. The interaction of magnetic impurities with electrons confined in one dimension has been studied by spatially resolving the local electronic density of states of small cobal…
We have studied the ordering dynamics of the striped patterns of a single layer of cylindrical block copolymer microdomains in a thin film. By tracking disclinations during annealing with time-lapse atomic force microscopy, we observe a dominant mechanism of disclination annihilation involving three or four disclinati…
Modulation doping of a semiconducting single-walled carbon nanotube along its length leads to an intramolecular wire electronic device. The nanotube is doped n-type for half of its length and p-type for the other half. Electrostatic gating can tune the system into p-n junctions, causing it to exhibit rectifying charac…