Materials Literature
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Porous silicon (PS) with its distribution of crystallite sizes is a highly disordered material. We present a theoretical formulation to explain the photoluminescence (PL) spectra of porous silicon. We base our formalism on the quantum confinement model using methods similar to those of Kane and Lifshitz. A minimal set…
By means of Monte Carlo simulations of a lattice model, microphase separation transition of symmetric diblock-copolymer melts confined in the thin-film geometry between parallel hard walls is studied. We impose a surface field which acts repulsively only on one of the two species, to stabilize lamellar order parallel…
The blue system of FeH, at 493 nm, has been recorded with a sample at near-ambient temperatures by laser excitation spectroscopy. With the help of dispersed fluorescence studies, all the strong lines in this region of the spectrum have been assigned to the (0,0) band of the g 6Φ–a 6Δ transition, where the lower state…
The measurement of the specific contact resistance, ρC, and microstructural analysis at the metal/diamond interface were carried out for diamond with various acceptor concentrations, NA, in order to understand the carrier transport mechanism at the metal/diamond interface. The ρC measurements were carried out for poly…
Magnetic properties of FeRh 1- x Pt x system with body-centered cubic and body-centered tetragonal (bct) structures were studied by means of X-ray diffractometry, magnetometry and Mössbauer spectroscopy, and the phase diagram in a temperature-composition plane was determined. With substituting Pt for Rh, the axial rat…
A lattice instability toward in-plane Kekulé and out-of-plane distortions is studied in metallic carbon nanotubes in both k · p approximation and tight-binding model. The k · p model Hamiltonian is given by Dirac's relativistic equation in the presence of distortion. The resulting gap equation is solved analytically i…
The thermal expansion and anisotropic magnetostriction of the RCo 2 Laves phases were studied in the temperature range 4-500 K using the X-ray powder diffraction method. In the heavy RCo 2 the magnetic moment of the itinerant d electron subsystem derived from the magnetovolume effect was found to fit well with the mag…
Empirical forms have been found for the total and differential elastic scattering cross sections for electron/atom scattering. The cross sections are valid over the range 0.1–30 keV and across the periodic table. The empirical forms of the cross sections are derived from trends in tabulated Mott scattering cross secti…
The 7\ifmmode\times\else\texttimes\fi{}7 surface has been studied with Si 2p core-level spectroscopy using an experimental resolution better than 70 meV at a temperature of 120 K. The spectra are much more well resolved than earlier reports and provide considerably more information. They consist of a bulk component an…
To verify the status of the divergence ${K}_{13}$ term in the elastic theory of liquid crystals we study submicron films placed onto an isotropic fluid substrate in the Langmuir trough (Langmuir liquid crystal, LLC). The upper and lower surfaces favor normal and tangential molecular orientation, respectively. The peri…
Complex perovskite A(B′B″)O3 ceramics with various degrees of B-site order have been structurally and spectroscopically characterized by means of x-ray diffraction, transmission electron microscopy, and infrared reflectivity. In Ba(Fe1/2Nb1/2)O3 and Pb(Fe1/2Nb1/2)O3, no order could be detected whereas Pb(In1/2Nb1/2)O3…
Hydrogen-, oxygen-, and nitrogen-related defects in chemical-vapor-deposited (CVD) diamond have been observed by infrared spectroscopy and found to affect optical absorptions in spectral regions of commercial interest. The origin of absorptions in the infrared spectrum at 2820 and 2833 cm−1, which have been observed p…
This paper addresses some important questions concerning hopping conduction in doped conducting polymers, i.e., dimensionality, homogeneity, adiabaticity, Coulomb interactions, and multiphonon character. It will be shown that electron transport in these materials is due to correlated hopping between polaronic clusters…
Ferroelectric capacitors having Pt bottom and top electrodes and a ferroelectric film of composition PbZr0.51Ti0.49O3 (PZT) were fabricated and investigated. The PZT films of thicknesses varying from 0.12 to 0.69 μm were prepared by organometallic chemical-vapor deposition. Annealed capacitors were investigated by cap…
We propose a family of nanotubules originating from a hexagonal ${\mathrm{BC}}_{2}$N sheet. Because of the anisotropic structure of the ${\mathrm{BC}}_{2}$N sheet, there are a variety of ways to obtain chiral structures by rolling the ${\mathrm{BC}}_{2}$N sheets into tubules. We performed first-principles and tight-bi…
A negative electron affinity (NEA) was found both experimentally by photoemission spectroscopy and theoretically by ab initio calculations for the 2\ifmmode\times\else\texttimes\fi{}1 reconstructed diamond (100) surface. This surface is the dominant growth surface for thin diamond films and can be obtained by chemical…
The ground-state electronic structure of NiO and MnO has been calculated within the Hartree-Fock approximation using local Gaussian basis sets. For both, a qualitatively correct ground-state electronic structure is obtained in which the wide-band-gap insulating character of these materials is seen to be a result of la…
Powdered samples of the type Ce1−xRExO2−y, where RE=La, Pr, Nd, Eu, Gd, and Tb, are synthesized over the range 0≤x≤0.5 starting from nitrate solutions of the rare earths. X-ray diffraction and Raman scattering are used to analyze the samples. These compounds, at least in the low doping regime and for strictly trivalen…
In this paper, the relationships between phenomenological and thermodynamic models used for characterization of insulating materials aged under multiple thermal-electrical stresses are derived. Phenomenological models fitting life lines for insulating materials that show or do not show a tendency to threshold are cons…
A practical review of the use of laser ablation for the deposition of thin films of oxide superconductors and metals is presented. Details of the design and operation of a laser ablation deposition system are discussed, together with the influence of operating parameters such as laser wavelength and power density on t…