Materials Literature
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The optical absorptions of anodically etched p+ and n+ porous silicon (PS) films were investigated by photothermal deflection spectroscopy. Si–H stretching overtones and combination bands of Si–F and Si–H were observed. The defect model in hydrogenated amorphous silicon was used to explain the Urbach edge and the subg…
In the literature a relation is often used that correlates Debye temperature and bulk modulus by a square-root law. It was recently shown that, for different cubic crystal structures, such a law is only fulfilled within relatively large error limits. If one takes, however, the average of the elastic constants of the t…
A wet thermal oxidation method is proposed to passivate the electrochemically etched porous silicon. Bright and stable photoluminescence is achieved by wet oxidation at relatively low temperatures of 400–500 °C. The Fourier transform infrared absorption shows that the formation of SiH(O3), SiH(SiO2), SiH2(O2) bonds ma…
In a comparative study we calculated the spin and orbital moments, spin and charge densities, and 4f crystal field (CF) parameters of the rare-earth transition-metal intermetallics ${\mathrm{Sm}}_{2}$${\mathrm{Fe}}_{17}$, ${\mathrm{Sm}}_{2}$${\mathrm{Fe}}_{17}$${\mathit{Z}}_{3}$ (Z=C,N), and ${\mathrm{Sm}}_{2}$${\math…
The aging characteristics of the electrostrictive lead magnesium niobate–lead titanate [(1−x)PMN–xPT] under dc bias field were investigated. It was observed that the amount of aging increases with the PT content for the compositions investigated (x≤0.3). For a fixed composition, the aging rate rises with temperature.…
The multiband envelope-function formalism---of which a convenient, analytical formulation is presented---is used to investigate the energies and wave functions of valence-band levels in spherical nanocrystallites of several III-V and II-VI compound semiconductors with finite spin-orbit splitting energy \ensuremath{\De…
Optical processes at the absorption edge in Y-doped BaCeO3 films with thicknesses of 160 and 4600 nm have been studied in the temperature region between 20 and 1000 °C. For the first time, optical band-gap energies of Y-doped BaCeO3 were determined with a room temperature value of 4.1 eV and a temperature coefficient…
Strong negative-electron-affinity effects have been observed on the surface of as-grown chemical-vapor-deposited diamond using secondary-electron emission. The samples were randomly oriented polycrystalline diamond films terminated with hydrogen. The effect appears as an intensive peak in the low-energy part of the sp…
A Kohn-Sham (KS) scheme for solids treating exchange exactly is introduced. The scheme emerges from a recently introduced exact formal KS procedure [A. G\"orling and M. Levy, Phys. Rev. A 50, 196 (1994)]. The exact density-functional exchange potential is obtained in terms of its Fourier components. The method can eas…
Mn-activated Zn2SiO4 and Ce-activated Y2SiO5 multilayer thin film electroluminescent (EL) devices were prepared by rf magnetron sputtering. The EL response of the devices under different voltages, frequencies, and pulse widths, as well as the transferred charge and decay characteristics were studied. The EL device usi…
We study the electronic structure of copper oxide clusters, ${\mathrm{Cu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ (x=1--4), using anion photoelectron spectroscopy and density-functional calculations. The experiment is used to successfully guide a computational search for the cluster geometries. The predicted electron affinit…
The electronic structures of the itinerant ferromagnets ${\mathrm{Cr}}_{1\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$Te (\ensuremath{\delta}=0.05, 0.25, and 0.375) have been studied by photoemission spectroscopy. The valence-band spectra are compared with the density of states given by band-structure calculat…
We present theoretical and experimental studies of the infrared (IR) spectroscopy, normal Raman spectroscopy (NRS), surface-enhanced Raman spectroscopy (SERS), and surface-enhanced hyper-Raman (SEHRS) spectroscopy of trans-1,2-bis(4-pyridyl)ethylene (BPE). This centrosymmetric molecule is expected to have no common Ra…
We present ab initio investigations of the structural and electronic properties of clean and hydrogen-covered diamond (100) surfaces within local-density-functional theory. Our calculations are based on a variational solution of the Kohn-Sham equations using a preconditioned conjugate-gradient approach and on the opti…
Using the LDA+U method (where LDA is local-density approximation) we show that a separate treatment of ${\mathit{t}}_{2\mathit{g}}$ and ${\mathit{e}}_{\mathit{g}}$ electrons on transition-metal sites as localized and itinerant, respectively, gives an appropriate description for the band structure of LaM${\mathrm{O}}_{…
Synchrotron x-radiation in a double-crystal geometry has been used for topography and rocking-curve measurements to study imperfections in single-crystal HP/HT synthetic diamonds grown from (111) seeds by the reconstitution technique. The influence that clusters of small opaque particles (sometimes called `pin-point-l…
In this paper we deal with a numerical model for the evaluation of the magnetic iron losses in one steel lamination. The magnetodynamic model for the magnetic field strength H is coupled with the Preisach model. The resulting boundary value problem for H is solved numerically by a modified finite element - finite diff…
Employing absorption, excitation and luminescence spectroscopy in a wide spectral range, the upconversion processes are investigated in at low temperature. From the detailed analysis of the spectroscopic data and the power dependence of the upconverted intensity, excited state absorption and energy transfer between ex…
The authors report the design, fabrication and characterisation of a planar gradient index (GRIN) PECVD lens. The PECVD-based heilcon plasma reactor was used to deposit graded layers onto a silicon wafer. Ray tracing and beam propagation methods were used to simulate the periodic refocussing of the nominally parabolic…
Zinc oxide ceramic varistors with simplified compositions show nonlinear current - voltage characteristics with in the range 45 - 130. Addition of enhances the nonlinearity tremendously and the concentration range of needed for high is around 3 mol%. Formation and involvement of a liquid phase during sintering is indi…