Materials Literature
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The copper salt of the amino acid α-amino isobutyric acid was synthesized and the crystal structure was determined by x-ray techniques. The crystals are monoclinic, space group P21/c (Z=2) with a=10.470(3) Å, b=5.335(1) Å, c=10.201(3) Å, and β=115.6(2)°. The magnetic susceptibility, measured between 1.4 and 12 K, show…
We investigated the diffusion of ion-implanted As in SiO2 with Rutherford backscattering spectrometry. By applying different annealing ambients and also encapsulating with a Si3N4 layer, we were able to distinguish three types of diffusion for implanted As in SiO2. These are correlated to two chemical states of As in…
The various electronic excitation channels which contribute to the production of photoelectrons and Auger electrons following x-ray absorption in a solid are discussed. In particular, we outline the contributions of elastic and inelastic photoelectrons and Auger electrons for the different electron-yield detection mod…
We derive a mathematical expression for the energy-loss spectrum or the energy distribution of electrons backscattered from a disordered film deposited on a substrate in terms of a primary scattering probability function corresponding to the elastic and inelastic scattering probabilities. Both single- and multiple-col…
We study linear polymer solutions containing different chemical species within the framework of the direct renormalization method introduced by des Cloizeaux. We study the osmotic pressure and polymer radii of dilute solutions containing two chemically different polymers A and B both in good and θ solvent when the int…
High‐velocity (∼2 to ∼5 km/sec) impacts into octahedrite iron meteorites (Gibeon, El Sampal, and Arispe), steel, and iron targets were made at the NASA‐Ames Vertical Gun Facility. The experiments clearly revealed the brittle behavior of meteorites at very low temperatures (<200° K) as indicated by spallation of the…
Polarized extended X-ray absorption fine structure (EXAFS) and near-edge spectra are measured on the Br K-edge for streteh-oriented trans -(CHBr y ) x . A large difference is observed in both the EXAFS and near-edge regions between the spectra with the polarization vector E parallel and perpendicular to the axis of or…
In compensated semiconductors, the occurrence of potential fluctuations which affect the local probability of ionization of deep levels cannot be ignored. These fluctuations strongly change the frequency and temperature dependence of the conductivity due to carriers in the bands. The expressions of ac and dc conductiv…
Metallic thermopower data on ${\mathrm{FeCl}}_{3}$-doped polyacetylene are presented. We compare the results with the data on iodine- and ${\mathrm{AsF}}_{5}$-doped polyacetylene in the heavily doped regime. General features of the results are consistent with those of a simple metal. However, details are different. We…
It is shown that a layer of liquid crystal molecules adsorbed on an evaporated SiO film plays an important role in aligning the bulk of the liquid crystal, apart from the topographical structure of the SiO film. On an SiO film evaporated from the substrate normal, various textural patterns were observed depending on h…
Luminescence spectra and decaytimes have been measured over a wide temperature range. Thermal equilibrium population between free and self-trapped excitons has been confirmed in both dimeric (α) and monomeric (β) forms of perylene crystals. Two-center type self-trapped exciton in α-perylene, and one-center type and tw…
Low-energy [(1-30)-eV] electron scattering in multilayer films of ${\mathrm{N}}_{2}$ and CO, and in Ar matrices containing ${\mathrm{N}}_{2}$, was investigated using high-resolution electron-energy-loss spectroscopy (HREELS) and one-dimensional multiple scattering theory. The films were formed by condensing the gases…
Raman spectroscopy has been used to determine built-up deformation in GexSi1−x/Si strained-layer superlattice grown by molecular beam epitaxy. By comparing peak positions in commensurate superlattices and single layers with those from incommensurate thick layers of the same composition we can obtain a quantitative det…
A systematic study of magnetocrystalline anisotropy of R2Fe14B tetragonal compounds with various rare-earth elements (R) has been carried out at room temperature by the pulse method. The anisotropy fields of Y2Fe14B and Nd2Fe14B compounds are 3.1 and 12 MA/m, respectively. The maximum anisotropy field of 28 MA/m was o…
We describe the most efficient semiconductor/liquid junction solar cell reported to date. Under W-halogen (ELH) illumination, the device is a 14% efficient two-electrode solar cell fabricated from an n-type silicon photoanode in contact with a nonaqueous electrolyte solution. The cell′s central feature is an ultrathin…
We have obtained polarized Raman spectra for vitreous silica densified at 3.95 GPa and 530 °C. The glass spectra show considerable changes on densification, which are discussed in terms of the observed reduction in average intertetrahedral bond angle and the central force model for connected networks. The results of t…
We have analyzed angle-resolved x-ray photoelectron spectroscopy data and found that large intensity enhancements along internuclear axes are due to forward-direction focusing of the electron beam by an attractive potential. Away from the internuclear axes, we found secondary peaks whose intensity is dominated by a st…
Slow crack growth data, molecular-orbital calculations, and vibrational spectroscopy results are used to develop an atomistic model for environmentally controlled fracture of silica glass. The model is based on chemically active bond defects generated by the strain field of the crack tip. Molecular-orbital results sug…
Optical reflectance studies of the $c$ face of pyrolytic boron nitride were carried out at room temperature in the photon energy range 0.45---10 eV. A Kramers-Kronig analysis was performed to determine the in-plane real (${\ensuremath{\epsilon}}_{1}$) and imaginary (${\ensuremath{\epsilon}}_{2}$) dielectric functions.…
A new, highly multiplexable liquid crystal display is described, which has a superior image quality than a twisted nematic display multiplexed at the same high level. The display cell consists of a chiral-doped nematic layer with tilted boundaries and a twist angle of ∼270°. It operates in a birefringent optical mode…