Materials Literature
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Atomistic pseudopotential plus configuration interaction calculations of the energy needed to charge dots by either electrons or holes are described, and contrasted with the widely used, but highly simplified two-dimensional parabolic effective mass approximation (2D-EMA). Substantial discrepancies are found, especial…
We have simulated the non-linear dynamics of networks of spin-transfer oscillators. The oscillators are magnetically uncoupled but electrically connected in series. We use a modified Landau-Lifschitz- Gilbert equation to describe the motion of each oscillator in the presence of the oscillations of all the others. We s…
Ultra‐thin fibers of zinc oxide (ZnO) were prepared by sol–gel processing and the electrospinning technique using poly(vinyl acetate) and zinc acetate as precursors. The fibers were characterized by thermogravimetric analysis, scanning electron microscopy, Fourier‐transfer infrared, and X‐ray diffraction, respectively…
Low temperature properties of ${\mathrm{BaZrO}}_{3}$ are revealed by combining experimental techniques (x-ray diffraction, neutron scattering and dielectric measurements) with theoretical first-principles-based methods (total energy and linear response calculations within density functional theory, and effective Hamil…
We report an in situ observation of water condensation and evaporation on lotus leaf surfaces inside an environmental scanning electron microscope. The real-time observation shows, at the micrometer length scale, how water drops grow to large contact angles during water condensation, and decrease in size and contact a…
Aluminum hydride polymorphs (alpha-AlH3, beta-AlH3, and gamma-AlH3) were prepared by organometallic synthesis. Hydrogen capacities approaching 10 wt % at desorption temperatures less than 100 degrees C have been demonstrated with freshly prepared AlH3. The temperature-dependent rate constants were determined by measur…
We calculate the magnetic interactions between two nearest neighbor substitutional magnetic ions (Co or Mn) in ZnO by means of density functional theory and compare it with the available experimental data. Using the local spin density approximation we find a coexistence of ferro- and antiferromagnetic couplings for Zn…
We theoretically demonstrate that at a finite temperature, an effective wall thickness of a single walled carbon nanotube (SWNT) should be $W=W_s+W_d$, where $W_s$ is the static thickness defined as the extension of the outmost electronic orbit and $W_d$ the dynamic thickness due to thermal vibration of atoms. Both mo…
Artificially fabricated structures with periodically modulated parameters such as photonic crystals offer novel ways of controlling the flow of light due to the existence of a range of forbidden frequencies associated with a photonic band gap. It is believed that modulation of the refractive index in all three spatial…
We study the presence of ferromagnetism in the phase diagram of the two-dimensional honeycomb lattice close to half-filling (graphene) as a function of the strength of the Coulomb interaction and doping. We show that exchange interactions between Dirac fermions can stabilize a ferromagnetic phase at low doping when th…
Large-scale Ni-doped ZnO nanowire (NW) arrays are grown. The electrical conductivity of a single Ni-doped ZnO NW has been increased for 30 times. The photoluminescence (PL) spectrum of the doped ZnO NWs has a red shift, suggesting possible doping induced band edge bending. The doped NW arrays could be the basis for bu…
We found direct experimental evidence for an orbital switching in the V 3d states across the metal-insulator transition in VO2. We have used soft-x-ray absorption spectroscopy at the V L2,3 edges as a sensitive local probe and have determined quantitatively the orbital polarizations. These results strongly suggest tha…
We investigate, for two water models displaying a liquid–liquid critical point, the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid–liquid critical point. We find a correlation between the dynamic crossover and the locus of specific heat maxima \documentclass[12p…
We show that post growth annealing of GaMnAs under As capping at temperatures in the range of 180-210 C leads to significant surface modifications. Depending on GaMnAs layer thickness and composition, we obtain either a smooth continuous reacted (MnAs) surface layer or 3D islands (quantum dots). The surface modificati…
Small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) were used to probe the final morphology of linear and novel branched poly(ethylene terephthalate) (PET) samples having undergone shear‐induced crystallization. The branched PET samples were produced via a reactive extrusion process designed…
In this study, an analysis has been made of electrochemical noise (EN) signals of potential and current obtained on immersing samples of the Alloy AA5083 (UNS A95083) in solutions of sodium chloride (NaCl). These signals have been processed using the calculation of the Hurst exponent, a tool derived from the theory of…
We studied the voltage–dependent liquid crystal (LC) dynamic stability corresponding to the pixel edge shape in the fringe field switching (FFS) mode. LC dynamics is very unstable near the edge of the pixel slit, where there is a horizontally different field direction compared with the active region, particularly when…
There has been extensive research activity since the discovery of fatigue free La-doped Bi 4 Ti 3 O 12 films on Pt electrodes. These films show superior ferroelectric properties and require a lower deposition temperature than the previously discovered SrBi 2 Ta 2 O 9 . Substitution of Bi by lanthanide elements other t…
In this research, a new method is developed for grading various types of yarn for appearance using image analysis and an artificial neural network. The images of standard yarn boards were analyzed by image analysis and four different faults factors were defined and measured for each series of yarn counts. For each ser…
In the variable pressure scanning electron microscope (VP-SEM) the incident electrons pass through a gaseous environment and the beam is scattered by these interactions. We show here that the experimental intensity profile of the scattered beam can be described as Gaussian in form to a high level of accuracy. This pro…