Materials Literature
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The dynamics of the infrared photoluminescence (PL) in silicon powder grown by plasma-enhanced chemical-vapor deposition (PECVD) of silane is reported. A nonlinear dependence of PL intensity on laser power of the form I a: P" with n as high as 7 has been found, indicating a multistep-multiphoton excitation process. T…
Neutron diffraction experiments on the Heisenberg antiferromagnet MnBr 2 were performed to study the successive magnetic phase transitions ( T N1 =2.32 K, T N2 =2.17 K). The magnetic structure in the intermediate phase is found to be a transverse sinusoidally-modulated structure with an incommensurate modulation vecto…
Local vibrational modes induced by defect complexes involving nitrogen and silicon impurities in different configurations are calculated using Keating potentials in a supercell model. Both the frequency and the vibrational amplitudes of atoms in the complexes are determined for each mode. It is found that defect compl…
Erbium-doped indium oxide films were prepared by rf magnetron sputtering. The Er-doped oxide films are conducting (or semiconducting) with a resistivity in the range of 10−3–103 Ω cm, and are optically active, i.e., show a clear room-temperature photoluminescence at 1.54 μm, corresponding to intratransitions in Er3+ i…
High-resolution x-ray-diffraction experiments show that the lattice parameter of porous-silicon layers expands when wetted by an alcohol or an alkane. This phenomenon is nearly reversible when the alkane is removed while there is a time-dependent drift during alcohol wetting. The experimental results obtained for seve…
We have performed simulations of liquid phases of phosphorus using the molecular-dynamics--density-functional method. Starting from a system of 26 ${\mathrm{P}}_{4}$ tetrahedra in a simple cubic unit cell of constant volume, we determine radial, angular, and defect distribution functions for the molecular liquid and f…
The Si(111)-7\ifmmode\times\else\texttimes\fi{}7 reconstruction is investigated by high-resolution core-level spectroscopy. A detailed line-shape analysis of spectra recorded over a wide photon energy range demonstrates the presence of four surface-derived components in the Si 2p line. These are attributed to the stru…
An adsorption system of metal-on-metal growth is presented. The adsorption of alkali-metal atoms on monolayers of dissimilar alkali metals preadsorbed on the Cu(001) surface has been studied by Auger-electron spectroscopy, work-function change, and low-energy electron-diffraction intensity analysis. We have examined t…
Study of the temperature and magnetic-field dependence of the negative magnetoresistance in the Mott variable-range-hopping regime is made on n-type ${\mathrm{CuInSe}}_{2}$. The relative magnetoresistance \ensuremath{\Delta}\ensuremath{\rho}/\ensuremath{\rho}(0) is found to be proportional to ${\mathit{T}}^{\mathrm{\e…
The electronic structure and relative stability of icosahedral ${\mathrm{Al}}_{12}$M (M=transition metal) clusters have been studied using the density functional theory within the local spin density approximation. Our calculations predict large binding energies for clusters with M atom in the middle of a d series in a…
Electrical resistivities along the ${\mathit{C}}_{2}$ and ${\mathit{C}}_{3}$ axes, Hall effect, Shubnikov--de Haas effect, and pulsed-laser-induced transient thermoelectric effect (TTE) have been measured in the temperature range 4.2--300 K for solid solutions of narrow-gap p-type ${\mathrm{Bi}}_{2\mathrm{\ensuremath{…
Induced absorption from the exciton state to the biexciton state was clearly observed under the site-selective excitation of the inhomogeneously broadened ${\mathit{Z}}_{3}$ exciton band in CuCl microcrystallites embedded in NaCl crystals. This allows us to obtain the size-dependent biexciton binding energy in CuCl qu…
We calculate the coherent electronic contributions to the third-order optical response ${\mathrm{\ensuremath{\chi}}}^{(3)}$(-\ensuremath{\omega};\ensuremath{\omega},\ensuremath{\Omega},-\ensuremath{\Omega}) of bulk semiconductors in the independent-particle approximation using a simple two-band model. The formalism us…
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…