Materials Literature
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Pulsed radiation of CO2 laser has been used to produce an optical breakdown on a silicon target in atmospheric air. After several breakdown initiations near the threshold of plasma production, a highly porous layer was formed under the radiation spot on the silicon surface. The fabricated layers presented the porosity…
Recystallization of nanocrystalline silicon in silicon oxide has been initiated with swift heavy ion irradiation. 100 MeV Ni ions from pelletron were used for irradiating the thin films of silicon oxide (SiOx) at fluences varying from 1×1012 to 5×1013 ions/cm2. Phase separation between silicon and silicon oxide is see…
Subwavelength electromagnetic focusing by a negative refractive index slab is shown to occur in a full wave numerical simulation of a causal, physically realizable negative index material. Limitations on the observability of this effect in simulations and experiments are discussed.
We have used Co K-shell near-edge and extended x-ray absorption fine structure to investigate the charge state and local structure surrounding Co in epitaxial Co-doped ${\mathrm{TiO}}_{2}$ anatase grown on ${\mathrm{LaAlO}}_{3}(001).$ Co is in the +2 formal oxidation state throughout the film, and substitutes for Ti i…
The direct observation of blocked polarization domains at the electrode–ferroelectric interface of electrically fatigued ferroelectric films is reported. Blocked nanodomains are believed to be the origin of polarization fatigue in ferroelectric nonvolatile memories but have not been directly observed so far due to the…
We present a novel colloidal route to photoluminescent CdS quantum dots and the doping of these nanoparticles with divalent manganese ions, resulting in emission caused by Mn2+ in addition to the band gap related emission of CdS. The semimagnetic semiconductor was synthesized using dithiol 1,2-bis(mercaptomethyl)benze…
We report the experimental characterization of porous silicon free-standing coupled microcavities. We have grown free-standing structures of up to 109 stacked layers. Free-standing structures are interesting because reflectance spectra can be measured on both sides of the samples. The comparison of reflectance spectra…
Abstract Cotton fabrics were treated by radio‐frequency plasma with tetrafluoromethane (CF 4 ) and hexafluoropropene (C 3 F 6 ) gases under different exposure times, pressures, and power levels. The hydrophobicity and water repellency were analyzed with measurements of the cosine of the contact angle (cos θ) and wet‐o…
The ability to predict the behavior of point defects in metals, particularly interstitial defects, is central to accurate modeling of the microstructural evolution in environments with high radiation fluxes. Existing interatomic potentials of embedded atom method type predict disparate stable interstitial defect confi…
29Si chemical shift anisotropy (CSA) data have been determined from (29)Si MAS NMR spectra recorded at 14.1 T for a number of synthetic calcium silicates and calcium silicate hydrates. These are beta- and gamma-Ca(2)SiO(4), Ca(3)SiO(4)Cl(2), alpha-dicalcium silicate hydrate (alpha-Ca(2)(SiO(3)OH)OH), rankinite (Ca(3)S…
Abstract Chitin was extracted from shrimp shells and then deacetylated to obtain chitosan. The degree of deacetylation of the chitosan was determined to be 0.76 using pH‐metric titration. A large number of cyanide functional groups were introduced onto chitosan by grafting with polyacrylonitrile as an efficient way of…
Photoluminescence lifetimes and optical absorption cross sections of Si nanocrystals embedded in SiO2 have been studied as a function of their average size and emission energy. The lifetimes span from 20 μs for the smallest sizes (2.5 nm) to more than 200 μs for the largest ones (7 nm). The passivation of nonradiative…
Previous studies of 5,10,15,20-tetraarylporphyrins have shown that the barrier for meso aryl-porphyrin rotation (DeltaG++(ROT)) varies as a function of the core substituent M and is lower for a small metal (M = Ni) compared to a large metal (M = Zn) and for a dication (M = 4H(2+)) versus a free base porphyrin (M = 2H)…
An empirical method based on chemical bond theory for the estimation of the lattice energy for ionic crystals has been proposed. The lattice energy contributions have been partitioned into bond dependent terms. For an individual bond, the lattice energy contribution made by it has been separated into ionic and covalen…
A systematic method to fabricate porous-silicon one-dimensional photonic crystals has been engineered to have a photonic bandwidth up to 2000 nm. The observation of the tailorability of the photonic band gap (PBG) underscores the requirement of the large refractive index contrast for making broad PBG structures. In th…
The structural, electronic, and magnetic properties of ultrathin Cu-coated Co nanowires have been studied by using empirical genetic algorithm simulations and a tight-binding $spd$ model Hamiltonian in the unrestricted Hartree-Hock approximation. For some specific stoichiometric compositions, Cu atoms occupy the surfa…
The experimental study of magnetic flux penetration under crossed magnetic fields in Bi2212:Pb single crystal performed by magnetooptic technique (MO) reveals remarkable field penetration pattern alteration (flux configuration change) and superconducting current anisotropy enhancement by the in-plane field. The anisot…
Short dangling bond wires (DB wires), fabricated on H-terminated Si(001) surfaces, show patterns of displacement that depend on their length. We have performed density function calculations, with and without spin-polarisation, designed to investigate the atomic and electronic structure of these wires. As expected, we…
Synchrotron x-ray scattering studies of anti-ferroelectric nanoregions (AFR) as fluctuations, which give rise to 1/2(hk0) superlattice reflections (alpha spots), were systematically performed in Pb(Mg1/3Nb2/3)O3 (PMN) ferroelectric relaxor. Separation of the alpha spots from underlying diffuse scattering background al…
Transient electric birefringence measurements were performed on dilute solutions of CdSe nanorods. The results confirm the existence of a permanent dipole along the c-crystallographic axis. Measurements on nanorods with different widths and lengths show that the longitudinal permanent dipole moment scales linearly wit…