Materials Literature
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It is well known that the electronic and optical absorption gaps of hydrogenated silicon nanoparticles are inversely proportional to the particle size. Here, the authors show that their optical emission gaps are remarkably different and dully dependent on the size for those smaller than 1.5nm, based on their excited-s…
Conversion of the Au∕n-ZnO contact from Ohmic to rectifying with H2O2 pretreatment was studied systematically using I-V measurements, x-ray photoemission spectroscopy, positron annihilation spectroscopy, and deep level transient spectroscopy. H2O2 treatment did not affect the carbon surface contamination or the EC–0.3…
A lateral on-chip electron-impact ion source utilizing a carbon nanotube field emission electron source was fabricated and characterized. The device consists of a cathode with aligned carbon nanotubes, a control grid, and an ion collector electrode. The electron-impact ionization of He, Ar, and Xe was studied as a fun…
Sixfold symmetry heptapodlike and threefold symmetry tetrapodlike ZnS structures have been fabricated by thermal evaporation of a ZnS and SiO mixture source in N2 at 1300°C. Both the heptapods and tetrapods have been formed by the self-assembly of ZnS nanowires with the preferred (0001) orientations. Structures and mo…
The authors demonstrate that photoinduced birefringence in azo-dye-doped polymers is strongly enhanced by hydrogen bonding between the guest molecules and the polymer host. The primary mechanism behind the enhancement is the possibility to use high dye doping levels compared to conventional guest-host systems because…
A series of Ga1−xMnxAs layers with high Mn compositions x (=0.075–0.200) has been grown and investigated. Magnetization, magnetotransport, and magneto-optical properties reveal that the layers have single ferromagnetic phase as in the case of typical (Ga,Mn)As. The authors also describe the variation of magnetic aniso…
Homogeneously aligned nematic liquid crystal (LC) cells doped with carbon nanotubes (CNTs) driven by an in-plane field were fabricated and their electro-optic characteristics were investigated. The effective cell retardation values showed no difference between doped and undoped LC cells in the absence of electric fiel…
This letter addresses the dependence of homogeneous dislocation nucleation on the crystallographic orientation of pure copper under uniaxial tension and compression. Molecular dynamics simulation results with an embedded-atom method potential show that the stress required for homogeneous dislocation nucleation is high…
The authors report the growth of carbon nanowalls in freestanding, three-dimensional aggregates by microwave plasma-enhanced chemical vapor deposition. Carbon nanowalls extrude from plasma sites into three-dimensional space. The growth is catalyst-free and not limited by nucleating surfaces. The growth mechanism is di…
Using time-resolved IR spectroscopy, we monitored the kinetics of folding and unfolding processes of a photoswitchable 16-residue alanine-based alpha-helical peptide on a timescale from few picoseconds to almost 40 micros and over a large temperature range (279-318 K). The folding and unfolding processes were triggere…
Using the B3PW hybrid exchange-correlation functional within density-functional theory and employing Gaussian-type basis sets, we calculated the atomic and electronic structures and thermodynamic stability of three double-layered (DL) $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}(001)$ surfaces: (i) SrO-terminated, (ii) $\m…
The variations in thermoelectric (TE) efficiencies æ of lead chalcogenide compounds (p-PbTe, n-PbTe, p-Pb0.55Te0.45, p-Pb1−xSnxTe1−y, p-PbSe, and p-PbS) at room temperature for the pressure P range of P∼0–10GPa are reported. A colossal (∼100 times) pressure-tuned improvement of æ is found for PbTe-based crystals under…
ZnO homojunction light-emitting diode with n-ZnO∕p-ZnO:As∕GaAs structure is produced by metal organic chemical vapor deposition. The p-type ZnO:As film is obtained out of thermal diffusion of arsenic from GaAs substrate with subsequent thermal annealing at 550°C. The n-type layer is composed of unintentionally doped Z…
Erbium-doped tellurite glasses are of great interest for the fabrication of active integrated circuits because of their unique properties in terms of bandwidth and rare earth solubility. The fabrication of multimode channel waveguides in a glass of this family, namely, a sodium-tungsten-tellurite glass, is demonstrate…
A Schottky ultraviolet photodiode using a (0001) ZnO single crystal grown by the hydrothermal growth method is reported. The photodiode consisted of a semitransparent Pt film for the Schottky electrode and an Al thin film for the Ohmic electrode. The photodiode had polarity dependences on current-voltage characteristi…
An effective model is developed to explain the phase diagram and the mechanism of magnetoelectric coupling in multiferroics, $RMn_2O_5$. We show that the nature of magnetoelectric coupling in $RMn_2O_5$ is a coupling between two Ising-type orders, namely, the ferroelectric order in the b axis, and the coupled magnetic…
Particle swarm optimization (PSO) is an evolutionary, easy-to-implement technique to design optical diffraction gratings. Design of reflection and transmission guided-mode resonance (GMR) grating filters using PSO is reported. The spectra of the designed filters are in good agreement with the design targets in a reaso…
The authors propose a simple physical model of threshold switching in phase change memory cells based on the field induced nucleation of conductive cylindrical crystallites. The model is solved analytically and leads to a number of predictions including correlations between the threshold voltage Vth and material param…
Piezoresponse force microscopy has been used to manipulate and image polarization of ferroelectric polymer Langmuir-Blodgett films at the nanoscale, achieving polarization control with a resolution below 50nm and imaging resolution below 5nm. Individual regions showed square polarization-voltage hysteresis loops, demo…
We present one inherent shortcoming of the LDA+U method in respect of its self-interaction correction of the LDA. By reexamining the mean-field approximation on the Hubbard energy in the Hartree-Fock form, we have derived a new expression for the ``double-counting'' energy which led to a more reasonable self-interacti…