Materials Literature
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A simple effective Hamiltonian for the electron-phonon coupling in the conjugated polymers is derived from the Su-Schrieffer-Heeger model with quantized lattice motions. Phonons correspond to lattice quantum fluctuations around the dimerized positions. Both acoustic and optical modes are considered. The energy-momentu…
The optical transitions of vanadium ${\mathrm{V}}^{4+}$(${3\mathrm{d}}^{1}$) on the hexagonal lattice site (h) of 6H-silicon carbide are studied by Fourier-Zeeman spectroscopy. The Zeeman splitting of the four zero-phonon lines is completely resolved. We first obtain the effective g factors from the Zeeman splitting.…
The natural mineral cetineite was prototype for the synthesis of the compound 1. Its nanoporous, template-free host structure is an idela object for numerous investigations. Electronic excitation and transport processes, for example, can be studied on this nanostructured semiconducting material. A part of the crystal…
The photoelectrochemical properties of a p-type silicon (100) electrode coated with tungsten oxide thin film were investigated as a function of annealing temperature. The variation in the annealing temperature affected the photocurrent of a WO3/p-Si electrode. A maximum photocurrent was obtained when the 500 Å WO3 thi…
Infrared transmission spectra were measured systematically in polycrystalline La1−xCaxMnO3−δ and several systems substituted by other rare earth (RE) ions such as Sm3+, Gd3+, Dy3+, etc., at La3+ sites or Fe ions at Mn sites but keeping the nominal Mn4+/Mn3+≈3/7. Two strong absorption peaks located around 600 and 350 c…
The \ensuremath{\pi}-electronic excitations of graphite layers are studied within the random-phase approximation. They principally reflect the \ensuremath{\pi}-band characteristics, the strong wave-vector dependence, the anisotropic behavior, and the special symmetry. The \ensuremath{\pi} plasmons in graphite have str…
We have used infrared (IR) absorption spectra to characterize a-C:H and its alloys (a-C:H,N,F). The samples were deposited in an rf plasma-enhanced chemical-vapor deposition system with various mixtures of ${\mathrm{CH}}_{4}$, ${\mathrm{N}}_{2}$, and ${\mathrm{NF}}_{3}$ gases. IR spectra are analyzed in detail and the…
In real metals with interacting conduction electrons a Fermi surface (FS) can no longer be defined as separating occupied from unoccupied one-electron states in k space, but is rather given by the location of discontinuities in the momentum distribution function n(k). Here we show that this many-body theoretical defin…
A comparative study of photoluminescence (PL) and photoluminescence excitation (PLE) spectra of porous silicon (PS) and Si oxide, both emitting blue light, is reported. The PLE spectrum of Si oxide monitored at 460 nm displays a three-peak structure with peak wavelengths around 265, 300, and 360 nm. The PLE intensity…
Extended x-ray-absorption fine structure (EXAFS), Fourier-transform infrared absorption (FTIR), and elemental analysis were used on a variety of CdSe nanocrystallites (NC's) to study surface structure. All CdSe NC's were grown by standard inverse micelle techniques. Two sets of NC's samples were made. One set was made…
The interaction of a Cl2 plasma with a Si(100) surface has been investigated by angle resolved x-ray photoelectron spectroscopy (XPS). It was found that the amount of chlorine incorporated into the near-surface region of Si increases with ion energy, and does not change with long exposure to the plasma. Chlorine is pr…
By employing a deep level transient spectroscopy (DLTS) technique, this work investigates the deep trap levels of rf-sputtered (Ba0.4Sr0.6)TiO3 (BST) thin films deposited at various temperatures. Arrhenius plots of DLTS spectra detect a single trap located at 0.45 eV in 450 °C deposited films, whereas two traps locate…
Strontium silicon trioxide has been synthesized for the first time and its structure solved. It is isostructural with the germanium analogue SrGeO3 reported by Hilmer [Sov. Phys. Crystallogr. (1963). 7, 573–576], but the true symmetry is monoclinic, rather than hexagonal as reported earlier. The structure has alternat…
The first stages of the oxidation process of titanium thin films deposited on top of Cu(100) substrates have been studied by means of Auger electron spectroscopy. Using principal component analysis we found different oxidation regimes for Ti films depending on their thickness. While for a film thickness up to 1 ML onl…
Dielectric dispersion measurements have been performed on CH 3 NH 3 PbX 3 (MAPbX 3 , X = Cl and Br) single crystals at frequencies between 50 Hz and 1 MHz. Significant dielectric dispersion was observed in the cubic and tetragonal II phases for MAPbCl 3 and in the cubic, tetragonal I and tetragonal II phases for MAPbB…
The carrier transport mechanism through the p-diamond/metal interface was studied by measuring specific contact resistances (ρc) using a transmission line method for Ti, Mo, and Cr (carbide forming metals) and Pd and Co (carbon soluble metals) metals contacting to the boron-doped polycrystalline diamond films. Schottk…
We determine the electronic structure of single-wall, multiwall, and filled carbon nanotubes using the local-density-functional formalism. In order to handle these extremely inhomogeneous systems of nested graphene cylinders with ${10}^{3}$--${10}^{4}$ valence electrons, we adopt a technique that discretizes the eigen…
The influence of n-type doping CdO with In or Y has been investigated by high-resolution ultraviolet and x-ray photoemission spectroscopy. It is found that core levels and valence band features suffer a shift to high binding energy due to doping. However this shift is less than the change in the width of the occupied…
The local electric fields in a semicontinuous metal film are shown to exhibit giant fluctuations in the visible and infrared spectral ranges, when the dissipation in metallic grains is small. The field fluctuations result in significantly enhanced Raman scattering from semicontinuous metal films. The scaling analysis…
A reproducible process for fabricating Ba1−xKxBiO3/Nb-doped SrTiO3 (BKBO/STNO) all-oxide-type Schottky junctions has been established, and the electrical properties of the junctions have been investigated at room temperature. Improving the STNO surface conditions by high-temperature oxygen-annealing made it possible t…