Materials Literature
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Porous silicon (PS) can be optically described as a homogeneous mixture of air, silicon, and, eventually, silicon dioxide, which explains the great tunability of its refractive index. This behavior makes porous silicon a very interesting material for the development of interference filters for use in optoelectronic ap…
Oxygen-deficient hexagonal BaTiO3 single crystals, with dielectric constant ε′∼105 and loss component tan δ∼0.13 at room temperature and a linear temperature dependence of ε′ in the range 70–100K, was analyzed by impedance spectroscopy analysis. Two capacitors, bulk and interfacial boundary layer, were observed, and t…
A photoaddressable azobenzene-side-chain polymer (see Figure) optimized to exhibit a large optical birefringence of Δn = 0.5 at 650 nm is described. The birefringence extends well into the telecommunication wavelength region, which, together with the high optical transparency above 650 nm, promises applications for in…
A wurtzite-structured CdSe nanosaw (see Figure) is formed by a two-step process: a fast-growth process along [010] creates the main ribbon, while a subsequent side-growth process along [0001] creates the one-sided teeth. The growth of the teeth is suggested to be a combined result of secondary epitaxial nucleation pro…
Parallel-plate Au(Pt)∕Ba0.25Sr0.75TiO3∕(Pt)Au thin film varactors were fabricated on high resistance Si substrates and characterized at dc, rf, and microwave frequencies. In the frequency range 10–45 GHz the varactors show relatively low losses, with loss tangent less than 0.025 at 45 GHz. Due to the thick and highly…
In this paper we develop a simple model based on a leaky transmission line to assess the electrical performance of transparent current spreading layers for application to surface light emitting diodes. Figures of merit suitable for device design are obtained and these are applied to a range of material systems reporte…
The primary energy dependecne and atomic-number dependence of backscattered electrons in Auger electron spectroscopy in the EN(E) mode have been investigated both theoretically and experimentally. A Monte Carlo simulation method with inclusion of cascade-secondary-electron production has been used to calculate the ful…
Magnetic films containing ordered arrays of holes (“antidots”) with period ∼200nm have been prepared using porous anodic alumina substrates with square and hexagonal symmetries. Large area (∼cm2) single-layer CoFe ordered antidot arrays show well-defined in-plane magnetic anisotropy related to the symmetry of the arra…
Single-phase perovskite structure BaZrxTi1−xO3 (BZT) (0.05⩽x⩽0.25) thin films were deposited on Pt–Ti–SiO2–Si substrates by the spin-coating technique. The structural modifications in the thin films were studied using x-ray diffraction and micro-Raman scattering techniques. Lattice parameters calculated from x-ray dat…
We report on the influence of a surface layer prevailing on perovskites on the piezoelectricity measured by piezoresponse force microscopy. Surface sensitive measurements show that this layer consists of chemisorbates and physisorbates. The surface layer can be removed to a large extent by heating the sample under ult…
We examine the intrinsic mechanism of ferromagnetism in dilute magnetic semiconductors by analyzing the trends in the electronic structure as the host is changed from GaN to GaSb, keeping the transition metal impurity fixed. In contrast with earlier interpretations which depended on the host semiconductor, it is found…
Here we report on the synthesis of ZnS∕SiC nanocables and SiC nanotubes and other relevant structures via a controllable two-stage thermal process using ZnS nanowires, nanoribbons, and sheets as templates. Within the cables, the ZnS cores are polytypes of fcc- and hcp-ZnS with ∼50–130nm diameter, and the SiC shells ar…
Diatoms are unicellular algae with ornate silica shells. Their dazzling ability to build tiny structures could inspire applications in the semiconductor industry, drug delivery, and engineering
A 3,4-ethylenedioxythiophene derivative bearing a viologen unit has been synthesized and electropolymerized to form the corresponding polymer (see Figure). Electrochemical and spectroelectrochemical studies showed that the polymer has the characteristics of both PEDOT and viologen, and possesses high electrochromic co…
In this letter, we report an important issue in nanoparticle synthesis by the “bottom up” approach. By controlling the pH of the starting mixture of the salts we have been successful in obtaining the desired conductivity of nanosized nickel ferrite. X-ray diffraction and transmission electron microscopy confirmed the…
A one-step synthesis of onion-like, shell-shaped carbon nanoparticles (SCNPs) is reported. Exposure of an acetylene flow to a continuous-wave infrared CO2 laser produces SCNPs with continuous bent-graphene layers in bulk quantity, but only above a threshold laser power.
In this work, we have studied the temperature dependence of a cholesteric liquid-crystal laser coupled to an optical fiber, with a view towards optical fiber sensor applications. To stabilize the laser emission, we developed a procedure to align the liquid crystal placed in the fiber. Unexpected oscillations in the la…
At liquid nitrogen temperature, the yield strength of nanocrystalline Ni and Co increases by as much as 50%–80% over the already-impressive (∼1GPa) room-temperature values. This unusual strength ratio as well as the remarkable magnitude of flow stress reached (as high as 2.5GPa) are unexpected for conventional close-p…
Zn 1 − x Fe x O thin films were grown on Al2O3(0001) substrates by radio-frequency magnetron sputtering. The alloys show wurtzite crystal structure up to x=0.24 with reduced c-axis lattice constant compared to that of pure ZnO. Fe 2p core-level photoemission measurements reveal the evidence for the coexistence of the…
The effect of the femtosecond and nanosecond UV laser irradiation (below the ablation threshold) on graphitelike hexagonal boron nitride (hBN) has been studied. Experiments were carried out with the compacted powder under high vacuum at room temperature using the excimer KrF laser (248nm). In the nanosecond operation…