Materials Literature
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We report the changes in surface state of tri- n -octylphosphine oxide (TOPO) capped CdSe nacocrystals by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the photobrightening state, where photoluminescence (PL) intensity increased during the illumination, surfac…
We report on a systematic experimental investigation of a class of multiferroic, three-phase particulate composite of Tb–Dy–Fe alloy, lead–zirconate–titanate (PZT), and polymer, in which a small volume fraction f of Tb–Dy–Fe alloy particles without and with the particle surfaces modified by an inactive surfactant are…
Polycrystalline Fe3O4 films have been prepared by reactive sputtering at room temperature. Transmission electron microscopy images show that the films consist of quite uniform Fe3O4 grains well separated by grain boundaries. It was found that the tunneling of spin-polarized electrons across the antiferromagnetic coupl…
Ge nanocrystals embedded in thermal SiO2 on top of a Si substrate are investigated using Raman spectroscopy and transmission electron microscopy. We observe that the Raman peak frequency of the Ge nanocrystals is strongly affected by compressive stress. In the case of large particles for which the phonon confinement-i…
Large quantities of very thin and wide single-crystal alpha silicon nitride (α-Si3N4) nanobelts were synthesized by a vapor-solid thermal reaction between ammonia and silicon monoxide (SiO) without using any added catalyst. Scanning electron microscopy, high-resolution electron microscopy, energy dispersive x-ray spec…
The resistivity of epitaxial ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ films deposited on ${\mathrm{SrTiO}}_{3}$ shows an upturn at low temperatures that is enhanced by the application of a strong magnetic field. This can be understood within the theory of quantum interference effects taking both the…
We report the effects of 30 and 50 keV Ga+ ion irradiation on the structure and electrical properties of arc-evaporated multiwalled carbon nanotubes (MWNTs). For 50 keV ions with doses of ∼1013 ions/cm2 the outer shells of the MWNTs remain intact, while the inner layers reorganize into highly ordered pillbox-like ∼5-n…
In the semicontinuum model of lattice vibrations in graphite proposed by Komatsu and Nagamiya, the expressions of the dispersion relation contain the elastic constants ${C}_{11},$ ${C}_{12},$ ${C}_{13},$ ${C}_{33},$ ${C}_{44},$ and \ensuremath{\kappa} and the interlayer spacing c as parameters, where $c\ensuremath{\rh…
Summary 1. Diatoms are recognised as indicators in temperate streams, but only recently have assessments begun of their value in indicating stream quality in the tropics and sub‐tropics. Here, we extend previous studies by assessing stream diatom assemblages in relation to water quality and habitat character in the Ka…
We propose a novel geometric approach to the description of the relaxation phenomena in complex condensed-matter systems. It is shown within a fairly general random site hopping model that the stretched exponential decay law, exp([-(t/tau)(beta)], originates from the simple and general geometric features of a random d…
Epitaxial synthesis and properties of novel Co and Mn-doped Ge magnetic semiconductors were studied. Epitaxial growth of high quality films with high doping concentrations has been stabilized by the use of two dopants. The magnetic and transport properties of the system exhibit high T(C) and large magnetoresistance ef…
A method is presented where the morphology of screen printed carbon nanotube pastes is modified using an adhesive tape. In this way, the organic matrix material is preferentially removed leaving an optimal emitter surface of sparsely distributed and well-aligned carbon nanotubes. From these emitter surfaces, homogeneo…
First principles total energy calculations were performed to characterize oxygen vacancy defects in tantalum pentoxide (Ta2O5). A simplified version of the crystalline orthorhombic phase of Ta2O5 was used in this study. Results indicate that O vacancies in Ta2O5 can be broadly classified based on their location in the…
Deep Inelastic Neutron Scattering measurements on liquid $^3$He-$^4$He mixtures in the normal phase have been performed on the VESUVIO spectrometer at the ISIS pulsed neutron source at exchanged wavevectors of about $q \simeq 120.0$ Å$^{-1}$. The neutron Compton profiles J(y) of the mixtures were measured along the $T…
According to the random first-order transition (RFOT) theory of glasses, the barriers for activated dynamics in supercooled liquids vanish as the temperature of a viscous liquid approaches the dynamical transition temperature from below. This occurs due to a decrease of the surface tension between local metastable mol…
Confinement of silicon nanoparticles in silicon nitride instead of an oxide matrix might materially facilitate its potential applications as a light-emitting component in optoelectronics. We report in this letter the production of high-density (up to 4.0×1012/cm2 from micrographs) silicon nanoparticles in SiNx thin fi…
When a composite of nonlinear particles suspended in a host medium is subjected to a sinusoidal electric field, the electrical response in the composite will generally consist of alternating current (AC) fields at frequencies of higher-order harmonics. The situation becomes more interesting when the suspended particle…
Cellulose fibers, in the form of a conventional filter paper, have been modified by reacting the hydroxyl groups on the fiber surface with 2-bromoisobutyryl bromide, followed by grafting using ATRP conditions. The papers were first grafted with methyl acrylate (MA), rendering the paper very hydrophobic as reported in…
We theoretically predict the thermal conductivity versus temperature dependence of Si and Ge nanowires. Three methods are compared: the traditional Callaway and Holland approaches, and our “real dispersions” approach. Calculations with the former two show large disagreements with experimental data. On the contrary, th…
We show that the thermal and electrical properties of single wall carbon nanotube (CNT)-polymer composites are significantly enhanced by magnetic alignment during processing. The electrical transport properties of the composites are mainly governed by the hopping conduction with localization lengths comparable to bund…