Materials Literature
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We present a realistic theoretical study of the surface-phonon spectra of diamond (100) surfaces. Our results reproduce the major features of the vibrational spectra of clean and hydrogenated diamond (100)-(2\ifmmode\times\else\texttimes\fi{}1) surfaces obtained from experiments. The reconstruction of the diamond (100…
Colloidal crystals of rhodamine labeled silica spheres dispersed in chloroform have been studied with fluorescence confocal scanning laser microscopy. We report the first determination of the three-dimensional crystalline stacking in the bulk of a concentrated dispersion. The structure was found to consist of a random…
We report on optical waveguide structures containing a thin liquid crystal (LC) film held between two photochromic command surfaces. The command surfaces consist of three monomolecular layers of a polymer with azobenzene side chains deposited according to the Langmuir–Blodgett–Kuhn technique. When exposed to light of…
We present a matrix formalism to describe the near-field diffraction pattern, at fractions of a Talbot distance, of a grating whose unit cell is composed of a discrete substructure. We show that this formalism is useful for designing Lohmann array illuminators.
We have developed a method for adding the effect of the surface barrier to the Van Hove--Tong suite of low-energy electron-diffraction programs enabling us to analyze very-low-energy electron-diffraction (LEED) spectra from complex reconstructed systems. The method models the effect of the surface-potential barrier on…
We use ab initio pseudopotential electronic-structure methods to describe successfully both the detailed static structures and the structural transformation in ${\mathrm{B}}_{2}$${\mathrm{O}}_{3}$ crystals. Employing a reduced cell volume, with full relaxation of all internal coordinates, our calculations model the st…
Detailed characteristics of photoinduced surface deposition (PSD) of metallic Ag have been studied using Ag-As-S bulk glasses to reveal the mechanism. The composition dependence of PSD in the AgxAs60−xS40 (25≤x≤45) system shows that the photosensitivity decreases with a decrease in the Ag content and becomes negligibl…
Abstract Positron Annihilation Lifetime Spectroscopy (PALS) measurements were conducted on polycarbonate subjected to either thermal expansion or to tensile and compressive strains. It was found that thermal expansion affected both the nanometer hole size and the hole number density, whereas mechanical stress affected…
The reversed-phase HPLC retention behavior of D-amino acid replacement sets of an amphipathic model peptide, neuropeptide Y, and corticotropin releasing factor has been studied. The results demonstrate that D-amino acid substitutions destabilized the amphipathic alpha-helix, leading to a decrease of fractional helicit…
Amorphous hydrogenated carbon films show a characteristic photoluminescence behavior that is of great interest for the study of their electronic structure. In the present paper we develop a model of the photoluminescence process in a polymerlike hydrocarbon on the basis of a mixed ${\mathit{sp}}^{2\mathrm{\ensuremath{…
We study solids of ${\mathrm{Si}}_{20}$ fullerenes, ${\mathrm{Si}}_{46}$ and ${\mathrm{Na}}_{2}$${\mathrm{Ba}}_{6}$${\mathrm{Si}}_{46}$, in the framework of density-functional theory. The electronic structure of ${\mathrm{Si}}_{46}$ is remarkably different from that of the diamond Si lattice due to its pentagonal netw…
Measurements are reported for the electrical dc conductivity of the semiconducting vanadium tellurite glasses containing P2O5, Sb2O3, or Bi2O3 in the temperature range 80–450 K. The experimental data have been analyzed in the light of existing theoretical models. It has been observed that the general behavior of the e…
The current-voltage characteristics of porous-silicon structures are presented and discussed. Evidence is given that the forward and reverse currents show Schottky-junction-like behavior. Experimental measurements of reverse I-V curves at different ambient humidities demonstrate that the reverse current depends strong…
The Urbach tail in crystalline GaAs and Si due to thermal vibration is evaluated in the temperature range 0--810 K. Recent experiments suggest that there is no thermally induced Urbach tail in undoped GaAs. This is most unexpected since thermally induced tails at the absorption edge having the Urbach form and widths $…
We investigate the band-gap narrowing in silicon caused by the introduction of additional electron carriers together with a neutralizing uniform positive background charge. The local-density approximation (LDA) is shown to be inadequate for calculating the band-gap narrowing. Using a first-principles technique and the…
Abstract The evolution of several structural characteristics during isothermal heat treatment of poly( p ‐phenylene terephthalamide) was studied. In this work, heat treatment was interrupted after different treatment times, with the specimens immediately quenched to room temperature. These specimens were then characte…
We have designed, fabricated, and tested a blazed artificial dielectric transmission grating in fused quartz for use at the 633-nm wavelength. By locally varying the index, using fabricated two-dimensional arrays of dielectric cylinders, we can achieve a desired phase modulation to produce a diffractive phase element…
We have performed a first-principles electronic-structure study of a planar structural form of a hypothetical ${\mathrm{C}}_{3}$${\mathrm{N}}_{4}$ solid and compared its energy to a fully three-dimensional form. We use a mixed basis of pseudoatomic orbitals and low-kinetic-energy plane waves to determine the single-pa…
The growth of ultrathin platinum films on a rutile ${\mathrm{TiO}}_{2}$(110) surface has been studied using low-energy ion scattering and x-ray photoelectron spectroscopy. In the temperature range between 160 and 420 K, Pt grows in three-dimensional islands on the ${\mathrm{TiO}}_{2}$ surface with the size of the isla…
We have developed a theory of one-phonon Raman scattering in semiconductor microcrystallites and quantum dots. In particular, we have given a complete description of the phonon modes of spherical structures embedded in another material, which includes a correct treatment of the mechanical and electrostatic matching co…