Materials Literature
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A systematic study is reported on the thickness dependence of the electrical resistivity in thin films of the giant magnetoresistance manganite Nd2/3Sr1/3MnO3. We observed a first-order phase transition versus thickness in these films, which is seen as a jump of about 30 K in the metal-to-insulator transition temperat…
This work describes the effects of pyrolysis oven length and erbium precursor on the preparation of discrete erbium-doped silicon nanoparticles. These doped nanoparticles were prepared by the co-pyrolysis of disilane and the volatile complex Er(tmhd)3 (tmhd=2,2,6,6-tetramethyl-3,5-heptanedionato). The particle sizes a…
Promising configurations for grating-waveguide structures are presented. In these structures, the grating layer, which is normally adjacent to the waveguide layer, is displaced by means of an intermediate layer, resulting in significant reduction of losses and weaker coupling. This leads to very narrow spectral bandwi…
We report on low-resistance ohmic contacts to the moderately doped n-type ZnO:Al(nd=2×1017 cm−3) obtained using Ti (30 nm)/Au (50 nm) metallization schemes. Annealed Ti/Au contacts exhibit linear current–voltage characteristics, showing that high-quality ohmic contacts are formed. The Ti/Au scheme produces a specific…
Large strain electrostriction in single-crystal ferroelectric materials is investigated. The mode of electrostriction is based on a combined electromechanical loading used to induce cyclic, 90° domain switching. Experiments have been performed on crystals of barium titanate with constant compressive stress and oscilla…
Time-resolved photoluminescence studies have been performed on (Cd,Zn)O/(Mg,Zn)O multiquantum wells, which are almost perfectly lattice matched (0.034%), grown by laser molecular-beam epitaxy on a ScAlMgO4 substrate. Radiative recombination of excitons in the wells exhibits a significant spectral distribution of times…
We carried out magnetotransport experiments under hydrostatic pressure in order to study the nature of the metal-insulator transition in BaVS$_3$. Scaling relations for $ρ(T,H,p)$ are established and the pressure dependence of the spin gap is determined. Our new results, in conjunction with a re-analysis of earlier sp…
Quantum Monte Carlo methods have proven to predict atomic and bulk properties of light and non-light elements with high accuracy. Here we report on the first variational quantum Monte Carlo (VMC) calculations for solid surfaces. Taking the boundary condition for the simulation from a finite layer geometry, the Hamilto…
A mechanical strain field applied to a monodomain cholesteric elastomer will unwind the helical director distribution. There are similarities with the classical problem of an electric field applied to a cholesteric liquid crystal but also differences. Frank elasticity is of minor importance unless the gel is very weak…
We report results of a Monte Carlo study of doped, diluted magnetic semiconductors in the low carrier density (insulating) regime. We find that the system undergoes a transition from a paramagnet at high temperatures to a ferromagnet at low temperatures. However, in strong contrast to uniform systems, disorder effects…
Structural transformations, electronic spectra and ballistic transport in pulled gold nanowires are investigated with ab initio simulations, and correlated with recent measurements. Strain-induced yield of an initial double-strand wire results first in formation of a bent-chain which transforms upon further elongation…
With the aim of reducing surface reflections and increasing the diffraction efficiency we investigated the superposition of subwavelength phase gratings onto blazed phase gratings. With direct-write electron-beam lithography bare blazed gratings and blazed gratings carrying subwavelength gratings were fabricated and t…
Abstract In this paper, the design and control of a novel shape memory alloy (SMA) actuator that possesses impressive payload lifting capabilities are presented. The actuator consists of 48 nickel-titanium SMA wires mechanically bundled in parallel forming one powerful artificial muscle. This new linear actuator can a…
Gas permeability is one of the key performance characteristics of polymeric films. Here we explore a novel approach for modifying the oxygen transmission rate of polymers by vapor deposition of melamine. We will show that melamine, upon physical vapor deposition, forms a transparent uniform layer on polymeric films su…
Chemical modification of argon-plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced surface graft copolymerization with glycidyl methacrylate (GMA), followed by epoxide-ring-opening reaction with aniline (An), and finally oxidative graft polymerization with aniline had been carried out to render the P…
“Blends” of 2,2‘-pyridil, (2-C5H4N)C(O)C(O)(2-C5H4N), and carboxylate ligands, R‘CO2-, in alcohols (ROH) at room temperature are used to produce three clusters of the general formula [Cu5(OH)2{(2-C5H4N)C(O)(OR)C(O)(OR)(2-C5H4N)}2(O2CR‘)4(ROH)2]. The five CuII atoms are coplanar, exhibiting a rectangular arrangement of…
The use of orotic acid (H 3 L) in iron(III) chemistry has yielded a structurally, magnetically, and spectrochemically very interesting complex. The 1:3:3 FeCl 3 ·6H 2 O/H 3 L/aqueous NH 3 reaction system in MeOH gives red (NH 4 )[Fe 3 (μ 3 -OH)(H 2 L) 3 (HL) 3 ]·7.75H 2 O ( 1 ) in high yield. 1 crystallizes in the hex…
A temperature-dependent photoluminescence study is reported for single crystals of M[Au(CN) 2 ] 3 and M[Ag(CN) 2 ] 3 (M = Tb; Gd; Y). The results indicate that in both Tb[Au(CN) 2 ] 3 and Tb[Ag(CN) 2 ] 3 exclusive excitation of the donor leads to sensitized luminescence for the acceptor, characteristic of the 5 D 4 →…
The objective of this study was to examine the mechanism of the reduction by hydrogen of ceria−zirconia (CZ) mixed oxides having a high BET surface area (100 m 2 g -1 ). Three methods were used in parallel to assess the Ce 3+ content, the surface and bulk oxygen vacancy concentrations, and the resulting oxygen storage…
In this article, a new hybrid model for estimating the pore size distribution of micro- and mesoporous materials is developed, and tested with the adsorption data of nitrogen, oxygen, and argon on ordered mesoporous materials reported in the literature. For the micropore region, the model uses the Dubinin−Rudushkevich…