Materials Literature
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The optical and electrical properties of Mn-doped epitaxial GaN were studied. Low-temperature optical absorption measurements indicate the presence of a Mn-related band with a well-resolved fine structure. The zero-phonon line is at 1.418±0.002 eV with a full width at half maximum of 20±1 meV. Two pseudolocal vibratio…
We formulate a Hartree-Fock-LAPW method for electronic band structure calculations. The method is based on the Hartree-Fock-Roothaan approach for solids with extended electron states and closed core shells where the basis functions of itinerant electrons are linear augmented plane waves. All interactions within the re…
Non-ionized media subject to strong fields can become locally ionized by penetration of finger-shaped streamers. We study negative streamers between planar electrodes in a simple deterministic continuum approximation. We observe that for sufficiently large fields, the streamer tip can split. This happens close to Firs…
We have investigated several ultra-thin copper nanobridges between supporting layers using a classical molecular dynamics simulation and a many-body potential function of the second-moment approximation of tight-binding scheme. This investigation has shown a part of the thermal properties of nanobridges, the tension i…
Wurtzite GaN:Mn films on sapphire substrates were successfully grown by use of the molecular beam epitaxy (MBE) system. The film has an extremely high Curie temperature of around 940 K, although the Mn concentration is only about 3 ~ 5 %. Magnetization measurements were carried out in magnetic fields parallel to the f…
The superconducting and structural properties of a series of Mg1-xAlxB2 samples have been investigated. X-ray diffraction results confirmed the existence of a structural transition associated with the significant change in inter-boron layer distance as reported previously by Slusky et al. Moreover,transmission-electro…
In this letter, we investigate the upconversion properties of 19ZnO–80TeO2–1Er2O3 glass after excitation into the I11/24 level using 980 nm radiation. At an excitation power density of 880 W/cm2, green emission [(2H11/2, 4S3/2)→4I15/2] dominates the upconversion spectrum with an efficiency of 0.16%. Temporal studies r…
Atomistic simulations using a combination of classical force field and density-functional theory (DFT) show that carbon atoms remain essentially sp(2) coordinated in either bent tubes or tubes pushed by an atomically sharp atomic-force microscope (AFM) tip. Subsequent Green's-function-based transport calculations reve…
Light scattering by individual Ag nanoparticles and structures have been studied spectroscopically. Individual particles were selected and manipulated with a micromanipulator installed inside a scanning electron microscope (SEM). With typical particle dimensions of some 100 nm, the plasma resonances of particles and t…
The cross-plane thermal conductivity of four Si/Si0.7Ge0.3 superlattices and three Si0.84Ge0.16/Si0.76Ge0.24 superlattices, with periods ranging from 45 to 300 and from 100 to 200 Å, respectively, were measured over a temperature range of 50 to 320 K. For the Si/Si0.7Ge0.3 superlattices, the thermal conductivity was f…
The observation of strong magnetoelectric effects is reported in layered composites of ferromagnetic lanthanum manganites and piezoelectric lead zirconate titanate (PZT). Studies were made on thick-film structures of ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ (LSMO)-PZT and ${\mathrm{La}}_{0.7}{\mathrm…
Giant magnetic-field-induced strain of about 9.5% was observed at ambient temperature in a magnetic field of less than 1 T in NiMnGa orthorhombic seven-layered martensitic phase. The strain proved to be caused by magnetic-field-controlled twin boundary motion. According to an analysis of x-ray diffraction data, the cr…
Electron paramagnetic resonance (EPR) and optical absorption spectra of Mn 2+ ions in alkali borotellurite glass systems have been studied. The EPR spectra of all the glass samples exhibit three resonance signals at g ≈ 2.0, g ≈ 3.3 and g ≈ 4.3. A six line hyperfine structure has also been observed at g ≈ 2.0. The con…
The derivation of effective equations for pressure wave propagation in a bubbly fluid at very low void fractions is examined. A Vlasov-type equation is derived for the probability distribution of the bubbles in phase space instead of computing effective equations in terms of averaged quantities. This provides a more g…
Microphase separation was induced from homogeneous polystyrene- block -polyisoprene (SI diblock) copolymer by grafting of a liquid-crystalline (LC) monomer onto the polyisoprene (PI) block. The origin of the formation of microdomain structure in the side-chain LC block copolymer from a homogeneous SI diblock copolymer…
The atomic charges derived from the extended electronegativity function, which includes the influence of bonding, were examined. These atomic charges were found to conform to an intuitive notion of atomic charge at the intermolecular, interatomic, and electronic levels. In addition, a new model for the core ionization…
We report differences in the thermodynamic behavior of compositionally symmetric ABC and BAC triblock copolymers near the order−disorder transition temperature and of binary ABC/BAC copolymer blends: poly(styrene- b -isoprene- b -dimethylsiloxane) (SID) and ISD with segment volume fractions near 0.33 and similar molec…
Polyethylene and isotactic polypropylene having 1,2- or 1,3-disubstituted cyclopentane structures were prepared by copolymerization of ethylene or propylene with cyclopentene (CPE) or 1,5-hexadiene (HD) using zirconocene catalysts. Effect of the cyclopentane structures on the melting point and crystalline structure of…
A new positive working photosensitive alicyclic polyimide precursor based on poly(amic acid tert -butyldimethylsilylester) ( 3 ) and 2,3,4-tris[2-diazo-1-(2 H )-naphthalenone-4-sulfonyloxy]benzophenone ( D4SB ) as a photosensitive compound has been developed. Polymer 3 was prepared by ring-opening polyaddition of bicy…
The crystallization behavior of functionalized polymethylene chains with carbamate esters placed periodically between alternating docosyl and octyl segments has been examined with infrared spectroscopy. Specific features of both the interactions and the chain conformation have been found. The crystallization kinetics,…