Materials Literature
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Magnetite (Fe3O4) films and multilayers were grown using plasma-assisted molecular beam epitaxy and result in single-phase films grown in registry with a MgO substrate. No evidence of interdiffusion is detected on as-grown films. Both structural and magnetic probes indicate behaviors expected for a magnetite thin film…
Oxygen K near-edge x-ray-absorption fine-structure (NEXAFS) of polycrystalline and film ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3\ensuremath{-}\ensuremath{\delta}}$ at room temperature was studied using fluorescence yield techniques. The bulk-sensitive nature of fluorescence yield (relative t…
A new and efficient synthesis of meso-linked porphyrin-quinone dyads and quinone-porphyrin-quinone triads has been developed via the intermediacy of porphyrins bearing 3-cyclobutenyl-1,2-dione and 3-(1-ethenyl)cyclobutenyl-1,2-dione substituents at one or two nonadjacent meso-positions. The free-base porphyrins 5-brom…
The temperature dependence of the current–voltage characteristics of Ba0.5Sr0.5TiO3 (BST) thin-film capacitors was studied from 300 to 433 K. An Au/BST/Pt/Ti/SiO2/Si structure was used. The BST films were deposited by rf magnetron sputtering. The conduction current was dominated by Schottky emission at room temperatur…
A microscopic model describing the electronic structure of carbon nanotubes formed from two-dimensional disordered graphite sheets is presented. The strong electronic-lattice coupling of states near the Fermi energy is shown to result in the formation of an energy gap. The model predicts that the energy gap in these t…
Hyperbranched polycarbosilanes were synthesized by hydrosilylation addition of methyldivinylsilane, methyldiallylsilane, triallylsilane, and methyldiundecenylsilane. Molecular mass distributions of the hyperbranched polymers were investigated upon systematic variation of the reaction conditions. The formation of hyper…
Optical absorption and photoluminescence (PL) measurements were performed on a series of hydrogenated silicon-nitrogen thin films deposited by plasma enhanced chemical vapor deposition covering a wide compositional range with the aim to find how absorption and emission processes are correlated. Our analysis indicates…
The unoccupied band structure of single-crystal graphite above the vacuum level is studied by very-low-energy electron diffraction. The position and dispersion of the three-dimensional bands coupling to vacuum, including the so-called interlayer state, are determined. The three-dimensional character prevails in the un…
We measured the complex dielectric constant in mats of single-wall carbon nanotubes between 2.7 K and 300 K up to 0.5 THz. The data are well understood in a Drude approach with a negligible temperature dependence of the plasma frequency ${\ensuremath{\omega}}_{p}$ and scattering time $\ensuremath{\tau}$ with an additi…
To gain insight into a recent observation that the prominent, Debye-type relaxation process observed for a primary alcohol may not be the α-relaxation process associated with molecular diffusion of a liquid [Europhys. Lett. 40, 549 (1997), J. Chem. Phys. 107, 1086 (1997)], the dielectric spectra of an uncrystallizable…
ATP is a ligand common to many proteins, yet it is unclear whether common recognition patterns do exist among the many different folds that bind ATP. Previously, it was shown that cAMP-dependent protein kinase, D-Ala:D-Ala ligase and the alpha-subunit of the alpha 2 beta 2 ribonucleotide reductase do share extensive c…
The heat capacity of poly(trimethylene terephthalate) (PTT) has been analyzed using temperature-modulated differential scanning calorimetry (TMDSC) and compared with results obtained earlier from adiabatic calorimetry and standard differential scanning calorimetry (DSC). Using quasi-isothermal TMDSC, the apparent reve…
The electron emission and structural properties of an isolated ``rope'' comprised of \ensuremath{\sim}70 individual single-walled nanotubes (SWNT's) were investigated by measuring the field-emission energy distributions and by using field-ion microscopy (FIM). Field-emission energy distributions, obtained under ultrah…
Band theory predicts a $(\ensuremath{\epsilon}\ensuremath{-}\ensuremath{\Delta}{)}^{\ensuremath{-}1/2}$ van Hove singularity in the tunneling density of states at the minimum energy $(\ensuremath{\Delta})$ of an unoccupied subband in a one-dimensional quantum wire. With interactions, an orthogonality catastrophe analo…
The synthesis of meso-linked quinone-porphyrin-porphyrin-quinone tetrads has been accomplished by the simple treatment of a CH2Cl2 solution of zincated 5-substituted-10,20-diphenylporphyrins (where the substituent = 3-cyclobutenyl-1,2-dione, various quinonyl derivatives, and p-anisyl) with 2,3-dichloro-5,6-dicyanoquin…
A detailed study of the unique optical properties of free-standing oxidized porous silicon films has been performed. Under continuous-wave laser irradiation, a strongly superlinear light emission and a very large laser-induced absorption are observed. The nonlinear emission is characterized by a sharp intensity increa…
Systematic measurements of the resistivity $\ensuremath{\rho}(T)$ and thermoelectric power $\ensuremath{\alpha}(T)$ under hydrostatic pressure have been made on single-valent perovskites of the family ${\mathrm{LnNiO}}_{3}$ $({\mathrm{L}\mathrm{n}=\mathrm{L}\mathrm{a},\mathrm{}\mathrm{P}\mathrm{r},\mathrm{}\mathrm{N}\…
From second-order Raman scattering we find that the maximum in the phonon density of states of single-walled nanotubes softens by 30 ${\mathrm{cm}}^{\ensuremath{-}1}$ over the value of graphite. A comparison of the phonon-dispersion curves of nanotubes in the literature shows that the ab initio approach best describes…
We study the development of the structure of crystals of colloidal hard spheres in time when gravity effects are minimal and polydispersity is small (<3%). The initial stacking of the close-packed hexagonal layers that make up the crystals is varied by applying various types of shear stress during nucleation of…
Having found much ambiguity in the infrared band assignments for polyamide 66 (PA66), we revisited some of these assignments before using infrared spectroscopy to assess microstructure changes resulting from multiple thermal treatments. We discovered that earlier assignments of the 1144 and 1180 cm−1 bands to the amor…