Materials Literature
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We report on the existence of MoS2 hollowed microtubes, several mm in lengths and less than 0.1 μm wall thickness, grown from the vapor phase. Scanning electron microscopy studies reveal that instability of thin weakly bonded sheets against folding causes the tube growth directly or indirectly beyond the formation of…
Zinc oxide (ZnO) films with c-axis orientation have been prepared on glass substrates by pulsed laser deposition with an ArF excimer laser. The fluctuations of c-axis orientation of the ZnO films are evaluated by full width at half-maximum (FWHM) of the rocking curve of the x-ray diffraction. The ZnO films with a FWHM…
Cellulose esters with linear aliphatic acyl substituents ranging in size from C12 (lauric acid) to C20 (eicosanoic acid) were prepared in homogeneous solution (DMAc/LiCl) using a novel synthetic method based on the use of a mixed p-toluenesulfonic/carboxylic acid anhydride. The resulting waxy cellulose esters had a hi…
The electronic structures for cubic ${\mathrm{WO}}_{3}$, ${\mathrm{LiWO}}_{3}$, ${\mathrm{NaWO}}_{3}$, ${\mathrm{HWO}}_{3}$, ${\mathrm{H}}_{2}$${\mathrm{WO}}_{3}$, and hexagonal ${\mathrm{WO}}_{3}$ have been calculated. The calculations rely on the local approximation to density functional theory and use a full-potent…
X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and ion scattering spectroscopy (ISS) have been used to study the Ag(111) single-crystal surface after exposure to ${\mathrm{O}}_{2}$ at high temperature and at atmospheric pressure. The activated formation of a strongly bound surface laye…
The effects of on-site Coulomb interaction in two-dimensional organic conductors, κ-(BEDT-TTF) 2 X, α-(BEDT-TTF) 2 I 3 and (BEDT-TTF) 2 MHg(SCN) 4 , have been studied within the Hartree-Fock approximation. If the strength of Coulomb interaction exceeds some critical value, various kinds of antiferromagnetic states app…
We study the conductance of metallic carbon nanotubes with vacancies and pentagon-heptagon pair defects within the Landauer formalism. Using a tight-binding model and a Green's function technique to calculate the scattering matrix, we examine the one-dimensional to two-dimensional crossover in these systems and show t…
The influence of postdeposition annealing on the structural and optical properties of rf sputtered insulating zinc oxide films has been investigated. The as-grown films deposited on quartz substrates were highly c-axis oriented and in a state of stress. These films become almost stress free after a postdeposition anne…
A new GaAs-based diluted magnetic semiconductor, (Ga,Mn)As, was prepared by molecular beam epitaxy. The lattice constant of (Ga,Mn)As films was determined by x-ray diffraction and shown to increase with the increase of Mn composition, x. Well-aligned in-plane ferromagnetic order was observed by magnetization measureme…
A parameterization of the optical functions of amorphous semiconductors and insulators is presented in which the imaginary part of the dielectric function ε2 is determined by multiplying the Tauc joint density of states by the ε2 obtained from the Lorentz oscillator model. The real part of the dielectric function ε1 i…
We study the electronic states of graphite ribbons with edges of two typical shapes, armchair and zigzag, by performing tight binding band calculations, and find that the graphite ribbons show striking contrast in the electronic states depending on the edge shape. In particular, a zigzag ribbon shows a remarkably shar…
Grain boundaries in copper doped with small amounts of bismuth have been examined by spatially resolved electron energy loss spectroscopy (EELS). The electron energy loss or x-ray absorption near edge structure (ELNES or XANES) yields information on the bonding state of the probed atoms. A white line was detected near…
Electrical switching behaviour of melt-quenched and glasses have been studied in the I - V mode, using a constant current source with incremental current steps. The samples are found to stay in the high-resistance OFF state up to a critical voltage (corresponding to a critical current ). Above , the sample switches to…
Valence electron energy-loss spectroscopy in a dedicated scanning transmission electron microscope has been used to obtain the interband transition strength of bulk . The interband electronic structure was obtained from critical point modelling. Comparison to established results from vacuum ultraviolet spectroscopy wa…
The study of internal interfaces using spatially resolved electron energy loss near-edge structure (ELNES) appears to allow the determination of local atomic environments and valence states of interfacial atomic species via a simple fingerprint formulism. Using the results of multiple scattering theory, this formulism…
A crucial first step in understanding the effect that internal interfaces have on the properties of materials is the ability to determine the atomic structure at the interface. Because interfaces can contain atomic disorder, dislocations, segregated impurities and interphases, sensitivity to all of these features is e…
The electrical properties of RF magnetron-sputtered aluminium-doped zinc oxide (AZO) films are studied. It is seen that the properties are closely related to their structural properties and doping incorporation. The highly conductive milky AZO films with a wedge-like surface consist of very small crystal grains. It is…
The direct longitudinal piezoelectric effect in lead zirconate titanate, barium titanate, bismuth titanate and strontium bismuth titanate ceramics was investigated with respect to the dependence on the amplitude of an alternating pressure. At low alternating pressure amplitudes, the behaviour of the piezoelectric char…
Samples of ZBLAN optical fiber were heated to the pulling and crystallization temperature in microgravity aboard a sounding rocket and on the ground at 1g. This was done in order to better understand the effects of gravity on the crystallization behavior of ZBLAN fibers. Samples heated in 1g at both temperatures cryst…
The hydrophilic monomer, acrylic acid (AA), has been grafted onto hydrophobic silicone rubber (SR) film via the γ-ray preirradiation graft technique. The AA percent graft in SR-g-AA film increases with increasing irradiation dose rate. The iron powder in monomer solution serves as one source of ferrous ion that is gen…