Materials Literature
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Blueshift of the band gap due to quantum confinement is calculated in a tight-binding model for a series of nine III–V zinc-blende AB (A=Al, Ga, or In, B=As, P, or Sb) and two diamond group-IV (Si and Ge) semiconductor clusters. Analytic expressions for the highest occupied molecular orbital and lowest unoccupied mole…
We report here a light-induced phenomenon—a self-induced rotation of the azimuth of elliptically polarized light passing through photobirefringent azopolymers. The experiments are carried out with films of amorphous and liquid-crystalline polymers. It has been shown that the induced rotation angle depends on the ellip…
Epitaxial Ca, Sr, and Pb doped manganite films of various compositions and thickness have been prepared to tailor metal-to-semiconductor phase transition to room temperature. Continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3 grown by the pulsed laser deposition technique were found to possess superior perfor…
Green upconversion emissions at 548 and 528 nm have been obtained from sol-gel derived nanocrystalline Er3+:BaTiO3 films under 980 nm excitation. The green emissions are attributed to the ground-state (4I15/2) -directed transitions from H11/22 (528 nm) and S3/22 (548 nm) of Er3+ ions. Analysis of the temporal evolutio…
A series of bulk polycrystalline La1−xAgxMnO3 samples with x ranging nominally from 0 to 0.5 were prepared by conventional solid-state reaction processing in air. X-ray diffraction patterns show that the samples contain a single perovskite phase when x⩽0.25, and are composed of two phases (a magnetic perovskite phase…
The structure of filamentous carbon formed upon catalytic decomposition of hydrocarbons on iron subgroup metals and their alloys is considered. The regularities of the deposition of carbon on these metals are generalised. The carbide cycle mechanism of carbon formation is considered in detail. The growth models of som…
Thick films of aligned single wall carbon nanotubes and ropes have been produced by filtration/deposition from suspension in strong magnetic fields. We measured mosaic distributions of rope orientations in the film plane, for samples of different thicknesses. For an ∼1 μm film the full width at half maximum (FWHM) der…
Point defects (vacancies, solute atoms, and disorder) are ubiquitous in crystalline solids. With in situ transmission electron microscopy we find clear evidence for the existence of a universal symmetry property of point defects; i.e., the symmetry of short-range order of point defects follows the crystal symmetry whe…
The dynamics of polymeric salt solutions are presented. The salt consists of chains $\rm A$ and $\rm B$, which are chemically different and interact with a Flory-interaction parameter $χ$, the $\rm A$ chain ends carry a positive charge whereas the $\rm B$ chain ends are modified by negative charges. The static structu…
Within the Kubo-Greenwood formalism we use the fully relativistic, spin-polarized, screened Korringa-Kohn-Rostoker method together with the coherent-potential approximation for layered systems to calculate the resistivity for the permalloy series Ni$_{c}$Fe$_{1-c}$. We are able to reproduce the variation of the resist…
In this paper we study reflection of holes in direct-band semiconductors from the linear potential barrier. It is shown that light-heavy hole transformation matrix is universal. It depends only on a dimensionless product of the light hole longitudinal momentum and the characteristic length determined by the slope of t…
Thin films of hydrogenated amorphous carbon (a-C:H) deposited by radio frequency plasma-enhanced chemical vapour deposition (rf-PECVD) have been studied for various applications. An interesting property of these films is their high breakdown strength (107 Vcm-1). This property of a-C:H can be exploited in high breakdo…
We propose a systematic, {\em a priori} approach to the problem of the calculation of solvation energies using continuum dielectric models coupled to quantum mechanical description of reacting molecules. Our method does not rely on empirically scaled van der Waals radii to create a dielectric cavity, but rather uses t…
Hydrogenated amorphous carbon (a-C:H), deposited by the rf-plasma enhanced chemical vapour deposition (rf-PECVD) technique, is a promising material for large area electronic and interlayer dielectric applications. The structural and electronic properties of rf-PECVD a-C:H, deposited at room temperature from CH4/He and…
Degassing of bundles of single-walled carbon nanotubes in vacuum at 500 K is found to drive the thermoelectricpower (TEP) strongly negative, indicating that the degassed metallic tubes in a bundle are n type. The magnitude of the negative TEP indicates that important asymmetry in the electronic carbon pi bands exists…
Dense, thick films of aligned single wall carbon nanotubes and nanotube ropes have been produced by filtration/deposition from suspension in strong magnetic fields. Electrical resistivity exhibits moderate anisotropy with respect to the alignment axis, while the thermopower is the same when measured parallel or perpen…
Zinc oxide, a wide-band-gap semiconductor with many technological applications, typically exhibits n-type conductivity. The cause of this conductivity has been widely debated. A first-principles investigation, based on density functional theory, produces strong evidence that hydrogen acts as a source of conductivity:…
We present a systematic trend study of the symmetric tilt grain boundaries about the <110> axis in molybdenum. Our results show that multiple structural phases, some incorporating vacancies, compete for the boundary ground state. We find that at low external stress vacancies prefer to bind to the boundaries in high co…
Synthetic methods for introduction of two substituents into the rings of octafluoroparacyclophane are presented. Nitration gives three isomers with nitro substituents on different rings: pseudo-ortho, pseudo-meta, and pseudo-para, in equal amounts. These dinitro compounds are shown to be precursors of a variety of oth…
Sandia National Laboratories (SNL) has produced limited quantities of fission-produced molybdenum-99 ( 99 Mo) within industry purity specifications using the Cintichem production process. Molybdenum-99 is produced by the irradiation of a target which has an electrochemically deposited layer of enriched uranium oxide.…