Materials Literature
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Interpretation of high-resolution electron-energy-loss (HREEL) spectra is dependent on knowledge of the applicable selection rules and therefore on the scattering mechanism involved. HREEL spectra from hydrogen-terminated C(100) demonstrate that impact scattering is the dominant mechanism and that dipole selection rul…
We report the frequency and the temperature dependence of the dielectric constant of polycrystalline ErFe 2 O 4-δ with different degrees of oxygen deficiency δ. A large dielectric relaxation, with the order of magnitude of 10 4 and nearly of the Debye type, is observed in the magnetically ordered states within the tem…
The linear electro-optic effect in short-pitch cholesterics is based on the linear coupling of the medium with an applied electric field. It has a number of remarkable properties. The electric field causes the optic axis to tilt in a plane parallel to the surfaces of the cell glass plates, giving the same symmetry as…
Binding energies and radiative lifetimes of excitons in crystallites are calculated with respect to size and temperature by using a tight-binding configuration-interaction technique. We discuss the recent proposal that, for porous silicon, the exchange splitting could be at the origin of the peculiar behavior of the l…
Li+ implantation at room temperature of insulating thin films of polycrystalline MgIn2O4 spinel (∼1.3 μm thick) was found to generate electron carriers efficiently. Li+ ions were implanted at 80 keV to a fluence of 1×1016 cm−2 and subsequently at 160 keV to the same fluence. Some implanted films were subjected to a po…
Electron-spin resonance and photoluminescence (PL) experiments have been performed on porous silicon. Results indicate the presence of oxygen shallow donors of binding energy in the 0.1-eV range, which show a distinct correlation with the intensity of the red PL observed in porous silicon. It is suggested that the sha…
Thin films of BaTiO3 have been epitaxially grown on Pt(001)/MgO(100) substrates by reactive evaporation. Structural and electrical properties were investigated as a function of film thickness. In situ reflection high-energy electron diffraction and cross-sectional transmission electron microscope observations have rev…
We present an approach to the calculation of absolute deformation potentials (ADP's) based on ab initio all-electron methods. The ADP of a given single-particle state is obtained from the variation of its energy between a compressed and an expanded region of the same material. Core levels are used to calculate the ban…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTColorimetric Determination of Carrageenans and Other Anionic Hydrocolloids with Methylene BlueHelena S. SoedjakCite this: Anal. Chem. 1994, 66, 24, 4514–4518Publication Date (Print):December 15, 1994Publication History Published online1 May 2002Published inissue 15 December…
The optical properties of carbon nanotubes are studied within the gradient approximation. The calculated dielectric function exhibits many divergent structures, due to the divergencies in its density of states. As a result, the electron-energy-loss spectrum has many peak structures, including a prominent one at \ensur…
The electronic states of the pristine and alkali-metal-intercalated monolayer graphite (MG)/Ni(111) systems are investigated by using angle-resolved ultraviolet photoelectron spectroscopy and x-ray-photoelectron spectroscopy (XPS). The electronic structure of the MG is modified largely by hybridization of the \ensurem…
First-principles and tight-binding electronic-structure calculations of hypothetical tubule forms of hexagonal ${\mathrm{BC}}_{3}$ have been performed. According to the total-energy and force calculations, stable atomic geometries of the ${\mathrm{BC}}_{3}$ tubules can be obtained by rolling hexagonal ${\mathrm{BC}}_{…
For Part I see ibid., vol.27, pp.852-60 (1994). A theoretical treatment based on a partly interactive trap system (PITS) described in Part I is applied to peak 5 of LiF:Mg,Ti. The model assumes two types of thermoluminescence traps for the given glow peak: (i) those which produce a linear response with dose and (ii) t…
Fast-anion-conducting glasses in the system xPbF 2 :(1-x)B 2 O 3 have been synthesized and analysed by thermal, electrical and spectroscopic techniques. The ionic conductivity ( sigma ) of these glasses is measured as a function of temperature and chemical composition by the complex impedance method and the results in…
The work consists in a taxonomic survey and classification of genera of blue green algae from soil and paving, which were found in eight samplis and conducted in five stations in the Campus or Universidade Federal de Santa Maria. Twenty two genera were obtained and distributed in five families and three orders.
The quantitative analysis of the properties of domain walls in Hg 2 Br 2 and KSCN is performed using the Landau-Ginzburg phenomenological description. The domain walls in KSCN are thin and possess high internal stresses in comparison with Hg 2 Br 2 . The interactions between domain walls have opposite characters in th…
The variance of the pair correlation function, the triplet correlation function, g (3) (r,s,t), and the three-body contribution to the configurational entropy, S 3 , were studied as possible tools for distinguishing between three different models of amorphous silicon (a-Si) with (nearly) identical pair correlation fun…
We have combined a technique for the lift-off of thin diamond films from a bulk diamond with a technique for engraving diamond with a focused excimer laser to produce free-standing single-crystal diamond microstructures. One microcomponent that has been produced is a 12 tooth gear ∼400 μm in diameter and ∼13 μm thick.…
Nanocrystalline Co0.5Fe2.5O4 has been prepared by mechanical alloying and subsequent vacuum annealing. Significant increase of coercivity was observed after a postannealing at low temperatures in air. Magnetic annealing resulted in anisotropic sample with a coercivity of 2.8 kOe and a remanence of 81% of the saturatio…
It is demonstrated that controlled high-strain-rate plastic deformation of heterogeneous reactive porous materials (Nb+Si, Mo+Si+MoSi2) produces shear localization. Within the shear bands, having thicknesses 5–20 μm, the overall strains (γ≤100) and strain rates (γ̇≤107 s−1) result in changes in particle morphology, me…