Materials Literature
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In this paper we analyze the optical absorption in porous silicon. This is the first attempt to explicitly demonstrate that it is not possible to extract the band gap of low-dimensional nanostructures like porous silicon from a Tauc plot of $\sqrt{\ensuremath{\alpha}\ensuremath{\Elzxh}\ensuremath{\omega}}$ vs \ensurem…
A subazaporphyrin (SubAP), tert -butylated and crowned subphthalocyanines (tBSubPc and SubCRPc), a μ-oxo dimer of tert -butylated SubPc {(tBSubPc) 2 O}, a subnaphthalocyanine (SubNc), and monosubstituted type unsymmetrical phthalocyanine (Pc) and naphthalocyanine (Nc) analogues have been synthesized. In particular, un…
This paper reports two fundamental observations on the size-dependent optical properties of colloidal gold nanoparticles. First, faceted gold nanocrystals in the size range of 63 ± 3 nm have been found to be highly efficient for surface-enhanced Raman scattering (SERS). These nanocrystals are identified from a heterog…
We present an efficient approach to describe the electronic transport properties of extended systems. The method is based on the surface Green's function matching formalism and combines the iterative calculation of transfer matrices with the Landauer formula for the coherent conductance. The scheme is applicable to an…
The compound [Fe(cyclam)(NCS)(2)](TCNQ)(2), where cyclam is 1,4,8,11-tetraazacyclotetradecane and TCNQ is a partially reduced 7,7,8,8-tetracyanoquinodimethane fragment, has been obtained from the corresponding thiocyanate by metathesis reaction. The compound crystallizes in the triclinic system, space group P&onemacr;…
Difunctional hydroxyl-terminated and vinyl-terminated poly(dimethylsiloxane) (PDMS) precursors with similar molecular weight distributions were used to synthesize end-linked networks in bulk with appropriate tetrafunctional cross-linkers. Composite PDMS elastomers from the same precursors were also synthesized with lo…
A conducting polymer, polypyrrole (PPy), has been deposited from aqueous media onto a submicrometer-sized poly(ethylene glycol)-stabilized polystyrene (PS) latex. Deposition experiments were carried out at two different initial pyrrole concentrations, and the latex concentration was systematically adjusted in order to…
An unusual temperature and concentration behavior of resistivity in $La_{0.7}Ca_{0.3}Mn_{1-x}Cu_xO_3$ has been observed at slight $Cu$ doping ($0\leq x \leq 0.05$). Namely, introduction of copper results in a splitting of the resistivity maximum around a metal-insulator transition temperature $T_0(x)$ into two differe…
Two kinds of cobalt-iron cyanides (Rb(0.66)Co(1.25)[Fe(CN)(6)].4.3H(2)O and Co(1.5)[Fe(CN)(6)].6H(2)O) with different electronic structures have been investigated to understand the photoinduced long-range magnetic ordering. Rb(0.66)Co(1.25)[Fe(CN)(6)].4.3H(2)O produces a photomagnetic effect, whereas Co(1.5)[Fe(CN)(6)…
Fine powders of Sm2(Fe0.9Co0.1)17Nx (x=∼3) with particle sizes (d) around 1 μm as coated with zinc metal produced via the photodecomposition of diethylzinc [Zn(C2H5)2], which still provided high remanence (Br) and coercivity (Hcj) values of ∼1.43 T and ∼0.85 MAm−1, were molded to compression-type resin bonded Zn/Sm2(F…
We have studied the magnetic and magnetotransport properties of the perovskites La8Sr0.2Mn8Ni0.2O3 and La0.7Sr0.3Mn0.8Ni0.2O3. Ferromagnetic cluster behaviors have been observed. The most interesting feature is that the cluster-glass state exhibits both macroscopic insulator-like transport behavior and largely enhance…
The adsorption of organic contaminants on a hydrogen-terminated Si(111) surface was investigated using attenuated total reflection Fourier transform infrared spectroscopy. When the hydrogen-terminated Si(111) surface was exposed to dry air, the sharp Si–H monohydride peak became weaker and a broad component became vis…
We prepared SrBi2Ta2O9(SBT) ferroelectric thin films on SiO2/Si and on MgO buffered SiO2/Si substrates using laser ablation, in situ annealing and postannealing, and observed retention time longer than 7 days. On SiO2/Si substrates, only the samples annealed at 800 °C occasionally exhibited good memory properties. On…
Using ab initio molecular dynamics we study pressure-induced hydrogen sublattice amorphization in $\mathrm{Mg}(\mathrm{OH}{)}_{2}$ and $\mathrm{Ca}(\mathrm{OH}{)}_{2}$. Our calculations reproduce the experimental behavior of these two systems, with $\mathrm{Ca}(\mathrm{OH}{)}_{2}$ showing significantly more marked eff…
We have performed a systematic ground state geometry search for ${\mathrm{Ge}}_{n}$ neutrals and cations in the $n\ensuremath{\le}16$ size range using density functional theory--local density approximation and gradient-corrected methods. Like their silicon analogs, medium-sized Ge clusters are stacks of tricapped trig…
We present a phase-field model for the dynamics of the interface between two inmiscible fluids with arbitrary viscosity contrast in a rectangular Hele-Shaw cell. With asymptotic matching techniques we check the model to yield the right Hele-Shaw equations in the sharp-interface limit and compute the corrections to the…
We implement a phase-field simulation of the dynamics of two fluids with arbitrary viscosity contrast in a rectangular Hele-Shaw cell. We demonstrate the use of this technique in different situations including the linear regime, the stationary Saffman-Taylor fingers and the multifinger competition dynamics, for differ…
We report on how electrochromic coloration is affected by oxygen deficient stoichiometries in sputtered amorphous tungsten oxide (a-WO3−y) films. The electrochromic coloration efficiency increases with increasing oxygen deficiency in (a-WO3−y) films. No coloration is observed in nearly stoichiometric WO3 films. Raman…
Direct adiabatic temperature change as well as magnetic measurements were carried out on two different samples of ${\mathrm{Gd}}_{5}{\mathrm{Si}}_{2}{\mathrm{Ge}}_{2}$ composition for which calculations predicted a ``giant'' magnetocaloric effect (MCE). While magnetic measurements well reproduce published values, serv…
Poly(ether sulfone) and poly(ether sulfone ketone) copolymers (I–V) were synthesized by the nucleophilic substitution reaction of 4,4′-dihydroxy diphenyl sulfone (DHDPS, A) with various mole proportions 4,4′-difluoro benzophenone (DFBP, B) and 4,4′-difluoro diphenyl sulfone (DFDPS, C) using sulfolane as solvent in the…